Remains of Los Alamos ‘missing scientist’ lead to possible murder or suicide: sources

The remains of a Los Alamos lab worker, recently discovered in New Mexico, have deepened the mystery surrounding his disappearance.

Melissa Casias, 53, left her home near Taos on June 26, 2025, and remained unidentified until her body was found by a hiker on May 28. Her case is linked to the 11 missing scientists in the US.

Casias’ body was found with bones, his sunburned remains leaning against a tree near a gun in the Kit Carson National Forest.

New Mexico State Police told The Post that his skull was fractured, but a CT scan did not reveal any projectiles in his skull.

Investigators are awaiting further autopsy results to determine the manner of death, according to spokesman Sgt. Ricardo Breceda.

The two most likely options now are suicide or murder.

“If that gun isn’t rusted and locked, I’m calling bulls-t,” said firebrand private investigator Thomas McNally, implying that if there was foul play the scene could have been a homicide.

According to local news reports, Casias’ clothes were burnt by the sun but his body appeared to have been eaten by wild animals, but this has not been confirmed by the police.

McNally, a former homicide detective and a Phoenix-based private investigator hired by members of the Casias family, who was born Casias, says the investigation into her disappearance was coordinated from the start.

“The State Police did not initiate any kind of search and rescue efforts. Melissa’s niece, Jazmin, had to find a local search and rescue organization. And then, in order for them to work, they had to get the permission and blessing of the State Police,” McNally told The Post.

NMSP described the area where Casias’ body was found as part of the park’s McGaffey Ridge, about 6 to 15 miles from Casias’ home in Ranchos de Taos, which Breceda said is a well-traveled, popular mountain area. However, it took almost a year to find the body. His family said in a statement that the place where he was found has been searched.

Despite his association with the missing scientists, both sides of Casias’ divided family agree on one thing – his work as an administrative assistant at Los Alamos National Laboratory had nothing to do with his disappearance, as speculated online.

Her husband Mark Casias, 61, and their daughter Sierra, 19, believe Melissa abandoned herself and may have taken her own life, but Melissa’s family, including her parents, sister and nephew, suspect foul play.

According to unidentified sources McNally spoke to, Mark – who also works in Los Alamos as a Superintendent in the maintenance department – is alleged to have asked neighbors if they had installed cameras in their properties shortly before his wife disappeared.

Two days after the disappearance, Mark reportedly noted that his wife may have lied about her death to the health insurance plan, according to one of McNally’s sources.

Mark could not be reached for comment by The Post. Los Alamos employees previously confirmed that he was on duty when Casias disappeared.

Police have yet to announce any suspects or persons of interest in Casias’ death.

“We are investigating this case in detail. It started as a missing persons investigation. Now that we have found his body, we are examining everything we have found and seeing where the evidence leads the investigation,” said Breceda.

Casias was last seen around 2:18 pm on surveillance footage, wearing a backpack and speeding eastbound alone on State Road 518 where his body was eventually found.

His mother, Joann Mondragon, previously told The Post that Casias liked to go for walks early in the morning, but was not known to do so on hot summer afternoons.

McNally says the woman in the video is not Casias and questions whether the time stamps on the video could have been doctored. Breceda completely rejected that speculation and said that the NMSP established the woman in that video as Casias.

Casias’ car was left parked outside his home and he left behind his keys, work cell phone, cell phone, wallet and purse. Both phones had been factory reset, but at different times, digital forecasts were revealed – one the night before and the other in the morning.

His reading glasses and 90 days worth of thyroid medication were not at home.

The Post has learned that two drops of human blood were found in an upstairs bedroom in the basement of Casias’ home, according to a source. Those samples are currently being tested for DNA.

But it may be too late to find more evidence, if any.

“They didn’t scan the entire master bedroom with luminol, that would have allowed them to see the high speed [blood] a gun, especially now that a gun has been found in the area where the body was,” said McNally.

NMSP has not confirmed or denied the bloodlines.

On the night of his wife’s disappearance, Mark wasted no time in speaking ill of his missing wife, according to interviews with Melissa’s family, the Mondragons, on the “Crime Junkie” podcast.

Mark said Melissa had been on a “roll with fk ups” recently, “ruined their finances,” racked up huge debts and fell behind on their tax payments, they said on the podcast.

The family also said that Mark admitted to them that he and his wife had an argument that morning because of Melissa’s smoking.

In recent interviews Mark has denied speaking ill of Melissa the night before she disappeared, calling the claim “absolutely untrue” and dismissing the vape fight as a petty marital dispute.

According to McNally, his sources said the couple often fight.

“Days before Melissa disappeared, Mark was asking the neighbors if they had cameras.” On the day Melissa went missing, a next-door neighbor heard screaming inside the Casillas’ home between 1:45 and 2 p.m.

“They also reported that they used to hear people crying, shouting and arguing when they left the house because they were fighting so often,” McNally said his sources told him.

According to records reviewed by The Post, the Casias were in dire financial straits. Both had garnishments on their salaries for unpaid taxes.

Mark says he didn’t know the extent of their financial problems until Melissa went missing, saying she was in charge of the family’s books.

The investigation into Melissa’s death is ongoing and has not been ruled a homicide. It should be noted that most of the accusations directed at Marku come from one side of the family who are divided among their friends.

Two days after Casias disappeared, Mark told the family that he might be “tied up” to let him collect the life insurance money, according to McNally.

“They were getting ready to search Melissa’s mom and dad’s house in Taos and Mark was there and in front of at least five other people, he said, ‘I know Melissa ran away and she doesn’t want to be found because she knows I can apply for life insurance at work,'” McNally said.

Police said Casias did not have active life insurance, but it was not known if Mark knew that. Court records reviewed by The Post show Mark filed a restraining order against McNally on May 18, who is still awaiting trial.

Mark said in interviews he gave later that he last saw his wife at around 6:15 in the morning when he left her for work. After 11 am he received a call from Melissa’s manager, which was the first sign to him that she was missing.

Casias’ disappearance grabbed the headlines because it happened at the same time as other disappearances related to aeronautics and nuclear research.

Former Los Alamos employee Anthony Chavez, 79, disappeared without a trace after leaving his home on foot on May 4, 2025, seven weeks before Casias.

Monica Reza, 60, an aerospace engineer who worked as director of NASA Lab’s Materials Processing Group, disappeared while walking in the Los Angeles forest shortly after two friends, and in June 2025.

Steven Garcia, a government contractor who works for a large facility in Albuquerque, also disappeared after leaving his home on August 28, 2025, with only a gun and no identification.

Maj. General William Neil McCasland, 68, has not been seen since he left his home in Albuquerque on Feb. 27. The FBI is now involved in the search for McCasland, who had deep knowledge of UFOs and was involved in the Pentagon’s most advanced aerospace research, the Post previously reported.