Teen obsessed with serial killer TV series Dexter bludgeoned mother

A misogynistic teenage boy who held his own mother hostage for hours before luring her to woods where he brutally murdered her with a hammer has been jailed for life. 

Tristan Thomas Roberts, 18, who admitted hating women, recorded himself keeping Angela Shellis, 45, prisoner in her own bedroom before duping her into going outside where he killed her. 

Ms Shellis, a teaching assistant, was discovered with severe head injuries beside a footpath near a nature reserve in Prestatyn, north Wales by walkers in October last year. 

In messages posted on online platform Discord posted later that day Roberts said: ‘I’ve just had the craziest day.’

He said that he had ‘beat the s*** out of her ‘ and described how he had ‘smashed her skull in so hard with a sledge hammer’.

Roberts was given a life sentence with a minimum term of 22 years and six months at Mold Crown Court on Wednesday after admitting her murder. 

Jailing him, Judge Rhys Rowlands said his mother’s terror during her last moments could not be imagined.

‘You appear to have revelled in the control you exerted over your own mother,’ he said. 

‘It was on any view a truly awful way for someone to die. 

‘It was made all the more dreadful that her attacker was her own son, someone it is clear she had cared for and indeed worried about in the weeks leading up to her death,’ he added.

He said Roberts ‘looked forward to inflicting pain’ and ‘enjoyed what you were doing’.

The judge said his mother would ‘no doubt have been terrified’.

‘Callously you ignored her pleas,’ he added.

‘She must have been truly terrified in these, the last moments of her life.’

Judge Rowlands said his ‘brutal’ actions had caused ‘dreadful anguish’ to his entire family.

He said the ‘sheer cruelty’ of his elaborate murder plot belied his young age, adding that despite his autism and ADHD diagnoses he knew exactly what he was doing that night.

Roberts, wearing a blue-green zip-up top, and flanked by two security guards, stared straight ahead from the dock as he was sentenced.

The court heard he had spent weeks researching the killing – and then digitally recorded the the last hours of his mother’s life.

Andrew Thomas KC, prosecuting, said: ‘These events were recorded by Tristan Roberts on his digital audio device.

‘He made a continuous recording, lasting more than four-and-a-half hours, covering everything from the initial assault to the fatal blows at the end.’

On the recording he said: ‘This is the moment we are doing it. We are going to hit her with a sledge hammer.’

The court heard he hit her with the hammer before strangling her.

Ms Shellis was conscious before speaking in a ‘calm and firm voice’ to phone 999 for medical help.

The court heard Roberts’s violent attack began at around 11pm and lasted until 3.30am. He recorded it on a voice recorder ‘too distressing’ to be heard in court.

Roberts – who was fascinated by TV serial killers – used AI search engines to research how to commit murder.

Immediately after turning 18 last October, he took advantage of being legally able to purchase knives to assemble an arsenal of weapons online and from homeware store The Range.

On the night of October 23 he recorded himself holding Ms Shellis prisoner in her own bedroom before leading her to a nature reserve and killing her with a hammer he had bought on Amazon.

The court heard how he spent hours on controversial gamer messaging app Discord. 

The platform has been accused in the US of harbouring radical communities including white supremacist far right groups.

Conservative activist Charlie Kirk’s suspected assassin, Tyler Robinson, is also reported to have been active on the site.

Roberts posted disturbing content that related to murder, violence, misogyny, weapons, and his intention to kill his mother.

He used multiple aliases on chat forums. His profiles had been flagged over his abusive and threatening content, including talking openly about killing his mother, described by relatives as having ‘a heart full of love and kindness’.

Roberts also had a fascination with serial killers, including TV series Dexter and movie American Psycho.

In the weeks running up to the murder he used AI search tool Deepseek to ask for tips for a ‘non-experienced killer’, including whether he should use a knife or a hammer.

After it refused to engage, Roberts tricked it by lying that he was writing a book about serial killers.

Although he has never explained the killing of his doting mother, and answered ‘no comment’ throughout his police interviews, in messages before the murder he said he was motivated by ‘hatred of women’.

Ms Shellis, a qualified teacher, had taken a teaching assistant post so she could spend more time at home with her two sons.

But in another message, Roberts wrote that he felt ‘abandoned, betrayed and bullied’ and blamed his mother.

He said that he was killing her for ‘revenge, justice, vengeance’ and so that he could move forward in his life.

In one chilling post about his mother he wrote how he had ‘nearly traumatised myself’ by going into her bedroom while she slept with a hammer in his hand.

The teenager bought weapons including knives, axes and hammers after turning 18 less than two weeks before killing his 45-year-old mother last October in Prestatyn, North Wales.

Relatives knew that Roberts regularly carried a knife in his backpack, and his mother had become increasingly concerned by his behaviour.

On October 17 – four days after he had turned 18 – she messaged a social worker and friends, stating that he had bought a knife and a hammer, Mold Crown Court heard today.

She had sought support for her son on numerous occasions and was again expressing concern as to his mental health.

In one note on her phone she asked: ‘Why?? What does he need these for?

‘Is he planning to hurt me, himself, what? Who? Why? FFS’.

Her older son was also concerned, and before going back to university he had set up wireless-enabled cameras inside the family home so they could monitor Roberts.

In the early hours of October 18, Roberts posted messages on Discord stating that he had been standing over his mother holding a hammer when she was asleep but did not use it.

The next morning, she wrote a note on her phone reading: ‘OMG… I did not sleep well at all… and Tristan kept coming into my room too – why?’

Another note read: ‘Am I safe in my room tonight?’

Her son put his murderous plan into practice after his older brother had gone back to university for the new term. 

The prosecutor said that on the evening of October 23, Roberts made a brief voice recording in which he said that he was going to kill his mother that night with a sledgehammer.

‘He said that he was ‘Alex’.

‘It is believed that he was in some way role playing.’

He taped himself saying: ‘This is Tristan Roberts.

‘Tonight I’m going to be Alex and I’m going to murder my mother with a sledgehammer.’

A four-hour recording started around 11pm.

It detailed an initial attack on the mother in her bedroom in which he attacked her to the head with a hammer and strangled her.

Shockingly, she was kept prisoner in her room for about four hours as her son brandished the weapon.

The recording – deemed far too harrowing to be played in court today – captures Ms Shellis pleading for him to call 999 and get help.

She remained calm, even saying she would ‘back him up and say that he had not known what he was doing’, prosecutor Andrew Thomas KC said.

He then cynically convinced her to leave the house under the pretence that she could have her injuries treated.

Instead he tricked her into taking a ‘short cut’ through a nature reserve where he took the sledgehammer out of his rucksack and began repeatedly attacking his screaming mother.

Roberts – whose previously long straight hair had been cut to a short crop before today’s hearing – cast his gaze downwards from his seat in the glass-panelled dock as the ‘catastrophic’ injuries he inflicted were spelt out.

But for most of the hearing he looked straight ahead, displaying no sign of emotion.

At one stage today’s proceedings had to be briefly halted after a relative of Ms Shellis began sobbing uncontrollably.

Ring doorbell footage from a neighbouring house showed mother and son leaving home on foot at 3.19am on the night of the murder.

The teenager returned to the semi-detached property alone at 5.35am before leaving again 50 minutes later, swinging a carrier bag thought to have contained bleach to clean the murder scene.

However his plans were thwarted by the presence of early morning dog walkers and he returned home again.

Here he logged on to Discord and ‘boasted’ about the killing, referencing the terrible injuries he had just inflicted.

Shortly after 8.30am, police were called to the discovery of a woman’s body in undergrowth at the Morfa nature reserve.

There was a lengthy trail of blood along a nearby gravel path, for more than 100 metres.

A murder probe was launched, with a cordon set up around the scene, but for four hours, detectives didn’t know her name.

A crutch, black gloves and black bloodied balaclava were discovered.

Shortly after 1pm a family member of Ms Shellis called police, worried about her welfare after reports of the woman’s body being discovered.

Originally from North Wales, she had moved back from Bedfordshire three years earlier after divorcing the boys’ father, getting a job as a teaching assistant at Rhyl High School.

It emerged she had needed a crutch because of a recent knee injury which meant she was temporarily off work.

Police arrested the teenager at the family home, where he had barricaded himself into his bedroom.

Roberts calmly asked officers: ‘Is the body you found my mother?’

Detectives later found CCTV footage showing the pair walking over a railway crossing towards the nature reserve with Roberts carrying a rucksack containing the murder weapon.

Police seized digital devices from his home – a laptop, voice recorder, and his mother’s mobile phone which was hidden under a suitcase in a wardrobe.

Family had tried to phone Ms Shellis after becoming concerned about her whereabouts.

Posing as his mother, Roberts replied to messages from his brother saying she couldn’t speak as she had a ‘bad throat’.

The brother messaged: ‘Just call me for a second… so that I know you are alive.’

Roberts replied from his mother’s phone to which the defendant replied: ‘I think I am alive [laughing emoji]’.

The laptop examination showed his extensive use of Discord including thousands of screenshots.

Roberts had made purchases on Amazon and at shops including The Range in preparation for the horrific killing.

Officers believe him turning 18 was significant because the sales would become legal.

Purchases included a balaclava, facemasks, overalls and clingfilm.

The murder weapon – a £20 ‘mini sledgehammer’ bought on Amazon – was seized at the family home.

A bloodstained water bottle in a carrier bag at the home had the mother’s DNA on.

Roberts was quizzed on nine occasions during four days after a mental health nurse deemed him fit for interview.

He answered ‘no comment’ to all questions and has never explained why he killed his mother.

He pleaded guilty to murder last month after a psychiatric report was discussed with him by his defence team in the cells.

A psychiatric report found ‘no credible evidence of any other form of mental disorder’ beyond his autism and ADHD.

‘His conditions did not impair his ability to understand his actions, form a rational judgment or exercise self control at all, let alone substantially,’ it concluded.

Powerful victim impact statements were read in court by her sister Sarah Gunther and surviving son Ethan.

He said their mother had done ‘everything’ for Tristan throughout his life, and had ‘put up with more than any mum should have’.

‘I don’t know how he could have done this to anyone, let alone the one person out of everybody who would do anything for him,’ he said.

‘She never gave up on him,’ he added, saying he felt Tristan had ‘manipulated’ professionals who tried to help.

In his statement – read on his behalf – Ethan said his brother’s crimes had ‘destroyed our family’.

He said he felt ‘haunted’ by anger over his mother’s killing as well as guilt that he was unable to protect her.

Ethan said he never wanted to see his brother again.

Reading hers in person, Ms Gunther said she wanted her sister to be remembered as ‘a mum who never gave up’.

She said Ms Shellis had been failed by agencies which should have helped the family and called for them to be held ‘accountable’, adding that it was a tragedy that ‘could have been avoided’.

Earlier the court heard how Ms Shellis repeatedly tried to obtain support for her son, but with ‘limited success’.

‘Their relationship became strained,’ Mr Thomas said.

Roberts spent time in hospital and in homeless accommodation before living with his father in Milton Keynes.

He returned to live with his mother in September 2025.

Roberts had a previous offence as a youngster for possessing a bladed article and wasn’t in education at the time of the killing. His older brother was away at university.

In mitigation, David Elias KC told the court that while his psychiatric state was no defence, his plan to murder his mother ‘must have been contributed to by his deteriorating mental health’.

He said Roberts had experienced a ‘traumatic childhood’.

Mr Elias asked Judge Rhys Rowlands to take into account his guilty plea and the fact he had just turned 18 at the time of the killing.

A safeguarding review is likely to take place. 

Afterwards Ms Shellis’s sister, Sarah Gunther, said the ‘devoted’ and ‘fiercely supportive’ mother had ‘fought tirelessly’ for Tristan and his brother.

She paid tribute to her as ‘a woman whose heart, strength, and spirit shaped the lives of everyone who knew her’.

Ms Gunther said: ‘She had so many amazing qualities, but one of the greatest was the way she devoted herself to her boys.

‘She was a fantastic and fiercely supportive mum, the kind who never gave up, no matter how hard life became.

‘She fought tirelessly for them, and her love for them was unbreakable, a source of strength that carried her and her boys through every challenge.

‘She will be missed every single day by so many people whose lives she touched.

‘But even though she is no longer with us in body, the love she gave and the memories she created will stay with us forever.

‘Her spirit lives on in the laughter she shared, the strength she showed, and the love she poured into her family.’

Senior investigating officer Temporary Detective Superintendent Andrew Gibson said Ms Shellis ‘showed tremendous bravery on that fateful night’ and ‘remained calm and continued to show her caring nature and love she had for Tristan, despite what must have been a terrifying ordeal for her’.

He added: ‘It was important that Angela remained the focal point throughout the investigation, and I hope today’s sentencing allows for some closure and supports Angela’s family in moving forward and towards rebuilding their lives.’

Andrew Slight of the Crown Prosecution Service said: ‘The level of planning Tristan Roberts did ahead of committing this shocking crime was elaborate and calculated.

‘His mother’s final moments must have been terrifying, yet he showed no concern or remorse for his actions.

‘The strong evidence presented by the Crown Prosecution Service painted a clear picture, showing Roberts’s intentions, resulting in his guilty plea.

‘Although this case has concluded, our thoughts remain with the family and friends who still feel the terrible loss of Angela.’