A California surfing instructor confessed to killing his two children with a spearfishing gun after abducting them, telling investigators that his belief in the conspiracy theories known as QAnon made him do it, authorities said Wednesday.

The father, Matthew Taylor Coleman, of Santa Barbara, drove his 2-year-old-son and 10-month-old daughter to Mexico over the weekend and fatally shot them Monday, according to an FBI investigator.

In a criminal affidavit filed in U.S. District Court in Los Angeles on Wednesday, the FBI special agent wrote that Coleman told authorities that he knew what he did was wrong, but that it was the only course of action that would save the world.

“M. Coleman stated that he believed his children were going to grow into monsters so he had to kill them,” the special agent, Jennifer Bannon, wrote. “M. Coleman explained that he was enlightened by QAnon and Illuminati conspiracy theories and was receiving visions and signs revealing that his wife, A.C., possessed serpent DNA and had passed it on to his children.”

Coleman described himself as an adherent of QAnon, the pro-Trump conspiracy movement whose followers hold, falsely, that a cabal of Democrats and coastal elites engage in pedophilia and worship Satan.

Coleman, 40, was charged Wednesday with foreign murder of U.S. nationals and remains in federal custody, authorities said.

A federal public defender who represented Coleman at a detention hearing Wednesday in federal court in Los Angeles, where he was ordered held without bond, did not immediately respond to a request for comment. Coleman is scheduled for arraignment Aug. 31.

The bodies of Coleman’s two children — identified in court records only by their initials: The girl was R.C. and the boy was K.C. — were found in a ditch by Mexican authorities, and they had large puncture wounds to their chest cavities, the FBI said.

Investigators said Coleman told them that his son was still alive after he shot him with the spearfishing gun and that he continued to move the spear around. He told an FBI agent that he had fired the spearfishing gun into his daughter’s heart, authorities said.

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