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Thursday, June 4, 2026

First missing scientist’s cause of death revealed in new account

The body of missing New Mexico mom Melissa Casias was found ‘skeletonized’ with a gunshot wound to the skull, propped up in a seated position against a tree in a remote part of the rugged Carson National Forest, the Daily Mail has learned.

Casias, who was 53, vanished from her Taos home in June 2025, leaving her phone, keys and purse behind. She was last seen alive walking east on the 518 Highway that leads out of the city towards the forest.

The case shot to national attention earlier this year amid conspiracy theories that her disappearance was part of a larger pattern involving individuals who had access to top secret government research.

Casias was an administrative assistant at the Los Alamos National Laboratory (LANL) – a facility located an hour from Taos and founded for the famed Manhattan Project during the Second World War that has been tied to nuclear weapons research ever since.

But Arizona-based investigator Thomas McNally, who has been working on the case on behalf of Casias’s parents, Joe and Joanne Mondragon, says her disappearance should never have been lumped in with other cases involving ‘missing nuclear scientists.’ He believes foul play was involved in her death.

‘It’s great that the press is getting this story out there because of the Los Alamos stuff,’ McNally said, ‘but it has nothing to do with [LANL]. If you want to tell the story, tell a real story.’

‘I want to be emphatic on this point – this is in no way, shape, or form related to her job.’

The discovery of Casias’s remains over the weekend has ended speculation over her whereabouts but has now created a new mystery over exactly what happened to her.

Melissa Casias worked at the Los Alamos National Laboratory, a nuclear research facility, before disappearing on June 26, 2025

Melissa Casias worked at the Los Alamos National Laboratory, a nuclear research facility, before disappearing on June 26, 2025

New Mexico State Police say Casias's body was found alongside a handgun in the McGaffey Ridge area of the Carson National Forest

New Mexico State Police say Casias’s body was found alongside a handgun in the McGaffey Ridge area of the Carson National Forest 

Although the New Mexico State Police are yet to release a cause of death, the Daily Mail has learned her body had a gunshot wound to the skull and a gun was found close by.

Casias was dressed in sun-bleached clothing and her body showed no signs of animal activity – unusual for remains left in the wilderness for a long period of time.

‘Her body was found May 28, in a very remote area of the mountains that is not normally frequented by hikers, people there for recreation,’ McNally explained.

‘The elevation is almost 8,000ft up. I understand that the skeletonized remains were found sitting up against a tree with bleached clothing, sun-bleached clothing.

‘There was a gunshot wound in the skull and a gun recovered at the scene.’

Police said the gruesome discovery was made by a hiker before cops recovered the remains from the remote spot and transported them to the medical examiner for an autopsy.

The results are pending and cops are yet to name any persons of interests or make any arrests in the case or determine what charges, if any, there should be.

But the Daily Mail can reveal that Casias’s devastated family believe the New Mexico State Police botched the case and left them to suffer in the dark about her fate for nearly a year.

Her husband Mark, who also works at LANL, told the family they had argued on their way to work

Her husband Mark, who also works at LANL, told the family they had argued on their way to work

Casias was last seen walking alone in New Mexico on June 26, 2025, after dropping off her husband at work at Los Alamos National Laboratory, but not reporting for work herself

Casias was last seen walking alone in New Mexico on June 26, 2025, after dropping off her husband at work at Los Alamos National Laboratory, but not reporting for work herself

Of the family’s reaction to the discovery, McNally said: ‘They have a lot of community support in town, which is great, but they’re broken and I think it hurts them even more now because they knew that they were right all along and the New Mexico State Police never went and did anything or looked for her.

‘They [the police] believed Mark (Casias’s husband) that she was running around with a boyfriend somewhere and she was a few miles down the road the whole f**king time.’

Casias’s parents and siblings have always insisted that she didn’t run off with a boyfriend and would never have left her much-loved daughter Sierra behind voluntarily.  

According to the Mondragons and McNally, Casias had been behaving normally around the time she went missing and went to work on the morning she vanished, accompanied by husband Mark who also works at LANL.

McNally said the couple got into an argument on the way with Mark telling Casias’s family it was over a vape pen.

Once there, Casias dropped Mark off and told him she had forgotten her badge so was returning home to work from there.

‘She got to the gate, dropped them off and said, “I forgot my badge. I’m going to go work from home,”‘ said McNally.

‘And we know she went home. We know she didn’t go into the office.’

Casias was one of four missing people with links to US defense and nuclear programs

Casias was one of four missing people with links to US defense and nuclear programs

Joe Mondragon and his wife Joanne have a private investigator working on their behalf and say her disappearance should never have been lumped in with other cases involving 'missing nuclear scientists'

Joe Mondragon and his wife Joanne have a private investigator working on their behalf and say her disappearance should never have been lumped in with other cases involving ‘missing nuclear scientists’

It is from there that things become murky. 

Casias did indeed return to Taos and was caught on camera dropping off a sandwich for Sierra. 

The final sighting of the mom was of her walking fast along the highway that leads to the forest.

When 19-year-old Sierra returned home that day, it was to find her mother gone while all her possessions had been left behind. 

‘She looked totally normal,’ McNally said of Casias in the final images ever taken of her. ‘Sierra said everything was fine. She didn’t look weird. 

‘Sierra got home at about 3pm from work. Her mom’s car was parked in front of the house, which wasn’t suspicious because she was supposed to be working from home. And the door was locked.

‘She went in and found Melissa’s purse, her old personal cell phone and the new phone that she had been using on the table, her wallet, keys, everything that you would take with you still there and Melissa nowhere to be found.’

The police were called around 8pm that night when Mark got home from work but, says McNally, made little progress despite signs of a struggle. 

McNally, a former homicide detective, said: ‘Melissa’s brother says he saw signs of a struggle in the yard out front, which if you look at the video of Melissa walking up the road as she’s leaving, she’s walking very briskly.

‘That would lead me to believe that she was fleeing somebody.’ 

As McNally predicted to the Daily Mail last month, the answer to the mystery did indeed lie in the Carson National Forest – a 1.5 million-acre rugged wilderness that includes the San Juan Mountains and the Sangre de Cristo range.

But the fact Casias’s remains have now been found and the mystery of her whereabouts ended has proved cold comfort for the Mondragons.  

‘I think them knowing that they were right exacerbates their pain that much more,’ said McNally.

‘I can tell you though, I think that that despair and sadness is kind of starting to turn into more of an anger and resolve to really make some people pay.

‘This story will most likely continue for quite some time.’

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