A Southern California man has been charged with killing his two young children with a spearfishing gun, deluded by QAnon conspiracy theories that made him believe that his kids were possessed with serpent DNA and that killing them would save the world, authorities said.

Matthew Taylor Coleman, 40, of Santa Barbara, was arrested Monday while reentering the U.S. from Mexico, where the bodies of his 2-year-old son and 10-month-old daughter had been found earlier that day, according to the criminal complaint.

Coleman, who founded a surf school in Santa Barbara, had been reported missing by his wife after she told authorities that he unexpectedly took off with their two children on Saturday while they were planning a family camping trip. He didn’t say where he was going, failed to answer her text messages and didn’t have a child’s car seat in his vehicle, she told authorities.

Still, she said she didn’t believe the kids were in danger at the time and thought her husband would come back, so she didn’t ask for assistance. When he didn’t return by the next day, however, she called the police and formally reported her family missing, according to the complaint.

Using a “Find My iPhone” app, authorities said they tracked Coleman’s phone to Baha California, Mexico, on Sunday afternoon. The next day, his phone was traced near an entry point along the U.S.-Mexico border. Federal authorities in San Diego were asked to meet Coleman upon his entry to the U.S. and check on the children’s welfare.

Coleman, however, was alone in his van, and Customs and Border Protection officers reported seeing what appeared to be blood on the vehicle’s registration paperwork.

Mexico authorities later reported to U.S. officials that the bodies of two children matching the missing kids’ description had been found that morning in a ditch with large puncture wounds in their chests.

In a recorded interview, authorities said Coleman confessed to killing his children and leaving their bodies in Mexico. He said he drove them across the border on Saturday, having “believed his children were going to grow into monster so he had to kill them,” according to the criminal complaint.

Coleman told authorities that he was “enlightened by QAnan and illuminati conspiracy theories and was receiving visions and signs revealing that his wife … possessed serpent DNA and had passed it onto his children,” according to the complaint.

Killing his children, he told investigators, would be “saving the world from monsters,” the complaint said. He knew it was wrong, “but it was the only course of action that would save the world.”

Coleman made his first court appearance in Los Angeles on Wednesday, charged with foreign murder of United States nationals. A public defender listed as representing him did not immediately respond to HuffPost’s request for comment.

QAnon supporters, among other things, believe that a group of Satan worshippers running a child sex ring are attempting to control U.S. politics and media. They reportedly believe that conspirators include top Democrats and Hollywood celebrities, and that former President Donald Trump was chosen as the hero to stop the conspiracy and bring the evil plotters to justice.

The Jan. 6 Capitol rioters included QAnon enthusiasts, and some Republican politicians, including Georgia Rep. Marjorie Taylor Greene, have expressed support for the outlandish ideas.

Prior to starting a family, Coleman competed with a national championship surf team, taught English in Spain and received a master’s degree from the University of California, Santa Barbara, according to his surf school website. The site features photos of him with his family.