'You'll See Mommy Soon:' Hotel Guest Recalls Seeing Matthew Coleman Hours Before He Allegedly Killed His Kids

On the afternoon of Aug. 7, 2021, Matthew Taylor Coleman was packing for a family trip with his wife, Abby. Suddenly, authorities say, he put his two kids — Kaleo, 2, and Roxy, 10 months — into his van and drove away from their Santa Barbara, Calif., home.

Crossing the border into Mexico, Coleman ended up at the City Express Hotel in the coastal city of Rosarito. He stayed there two days before, authorities allege, he took Kaleo and Roxy to a nearby ranch and killed them with a fishing gun.

It's unclear what Coleman did during his time at the City Express Hotel, but another guest tells PEOPLE that she saw the Coleman family in the lobby just hours before the children died.

"They stood out to me because they were really good looking, and I wondered where the mom was," says Malena Rivas, who stayed at the hotel for a week in August. Rivas showed PEOPLE a receipt that confirms that her hotel stay overlapped with the Colemans. "I just assumed that she was already down at the pool or something," Rivas adds.

According to Rivas, nothing about Coleman's behavior seemed out of the ordinary. "He was talking to them, smiling, and it was normal to me. He said 'You'll see mommy soon' or something like that, which is why I thought she was there with them, either at the pool or up in their room."

But Abby was 250 miles away at the family home in California.

When Matthew drove off with the kids, she called police out of concern. According to an FBI report obtained by PEOPLE, she told authorities that she and her husband had not been arguing and that there was no marital strife. She told cops that she did not believe that the children were in any danger and that she thought Matthew would eventually return home with the kids.

But the children never came home. Authorities allege that after two days at the hotel, Coleman went to a nearby ranch and killed them with a spearfishing gun. Their bodies were discovered later that morning by the ranch owner.

Coleman was arrested as he attempted to cross the border into the U.S. According to an FBI criminal complaint obtained by PEOPLE last August, he told authorities that was allegedly motivated by various outlandish conspiracy theories.

"He said visions and signs revealed that his wife, A.C. [Abby Coleman], possessed serpent DNA (M. COLEMAN mentioned that he was not sure if his wife was a shapeshifter) and had passed it onto his children and that all things were pointing to the idea that his children have corrupted DNA that will spread if something is not done about it," reads an affidavit.

Authorities allege Coleman believed in the QAnon conspiracy theory, which includes the false belief that former president Donald Trump has secretly been battling a cabal of Satan-worshipping pedophiles at the highest levels of political power and influence.

In a later affidavit, Abby allegedly told authorities she had also researched QAnon with her husband, but said he "became significantly more paranoid that people around him were involved in a conspiracy." Friends told PEOPLE earlier this year that Coleman spent hours a day on websites and message boards, reading about conspiracy theories.

Coleman has pleaded not guilty. PEOPLE has not been able to reach his public defender.

Rivas tells PEOPLE that she has thought about the Coleman family every day since seeing them at the hotel.

"I keep wondering if there was some clue I missed that should have been fishy to me," she says. "I wish I had gone up and said hello, just to figure out what was going on and maybe to help. But I just didn't know that anything was wrong. I just didn't know."