The jailhouse letter that Matthew Taylor Coleman sent to a friend in late May gives more clues to the state of mind of the California man who allegedly killed his two children in Mexico with

a spearfishing gun. The two-page handwritten letter addresses some of his alleged conspiratorial thinking — including his belief that his wife, Abby, had reptile DNA that she passed down to

the couple's kids, Kaleo, 2, and Roxy, 10 months. Coleman has been charged with two counts of foreign first-degree murder of United States nationals, and has pleaded not guilty.

"With God's help, I'm realizing how far away I was from the Truth," Coleman wrote in the letter, which was viewed by PEOPLE. "I shouldn't have spent so much

believe, but I don't have access to information anymore, so I'm having to use my mind to figure things out." "It's a good thing," he continued. "There was

so much noise and so much confusion, and a lot of that is gone now." On Aug. 7, 2021, Matthew and Abby were packing for a family trip. Authorities allege that Matthew abruptly put Kaleo

and Roxy into his van and drove away from their Santa Barbara, Calif., home. Abby called police out of concern. According to the FBI's report, 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 he didn't return, instead allegedly driving the children into Mexico. Two days later, authorities allege, he took the kids to a ranch, where he killed

them with a spearfishing gun and returned to his hotel a few hours later. He was arrested when he attempted to cross the border back into the U.S. According to an FBI criminal complaint

obtained by PEOPLE last August, Matthew 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," according to the affidavit. Authorities allege Coleman believed in the QAnon conspiracy theory, which

holds 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 the conspiracy theories. PEOPLE has not been able to

reach Coleman's public defender.