A man who has been accused of killing his children with a spear gun in Mexico allegedly did it due to his belief in QAnon conspiracy theories.

Matthew Taylor Coleman, 40, drove his 2-year-old son and 10-month-old daughter into Mexico on Saturday, August 7. His wife reported him and their kids missing the following day. Investigators believe that the accused took the children to a ranch in Mexico early on Monday morning, killed them with a spearfishing gun, and returned to his hotel a few hours later.

The children's bodies were found by a farmer just hours after they were killed. After their father emerged as the suspect, agents with Baja California's State Security and Investigation Guard alerted U.S. authorities warning that he would likely be heading back to the States. American border officers stopped him as he approached the San Ysidro Port of Entry and arrested him on the spot, reports People.

The man has been charged with foreign murder of U.S. nationals. He is being held without bond and is yet to enter a plea. Upon his arrest, he told the police that QAnon conspiracy theories, according to which his kids had "serpent DNA" and needed to be killed to save the world, were the motive behind his crime.

Friends of the accused confirmed that he believed in some weird theories, but said that they never suspected he was capable of violence. A friend who would regularly workout with Coleman recalled about their conversations regarding parenting, "The conversations were pretty typical. Feedings, diapers, the basic stuff you'd expect of a guy with a newborn and a toddler. But he was so happy, so excited about his family."

However, the friend revealed that the conversations steered towards the darker side by this year. "He'd tell me about stuff he read online. Conspiracies. But he'd present it like, 'I read something really crazy. Isn't that ridiculous? But then, he'd start adding things like, 'yeah, but when you think about it, it all makes a lot of sense,'" the friend said.

"It was like he was starting to believe them. And he spent a lot of time looking at these conspiracies. He devoted a lot of brain power to them. It became clear to me that he believed some weird stuff," he added.

The pal made it clear none of the things that Coleman said suggested that he was a danger to himself or anyone else. "We're all pretty conservative, and this was not just conservative political talk. This was just out there. Stuff that made zero sense to me," the friend said, adding that people in the accused's circle are "devastated" with the news.

"Plenty of people believe plenty of things that aren't mainstream and they never get violent. So why did this happen? It's just really sad," the friend said.

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Crime scene police line | Representational Image Photo: GETTY IMAGES / SCOTT OLSON