A Santa Barbara, California, surf school owner was indicted Wednesday for allegedly killing his 2-year-old son and his 10-month-old daughter with a spearfishing gun last month in Mexico.

Matthew Taylor Coleman was charged with two counts of foreign first-degree murder of United States nationals and is eligible for the death penalty.

"The murder of a child is difficult to understand under any circumstances," Kristi K. Johnson, the Assistant Director in Charge of the FBI’s Los Angeles Field Office, said in a statement. "I’m proud of the quick investigative efforts by FBI Agents, the Santa Barbara Police Department, U.S. Customs and Border Protection and our Mexican counterparts which led to the arrest of Mr. Coleman as he entered the United States, and I look forward to delivering justice for the young victims and their family."

Coleman’s wife, Abby Coleman, reported her husband had left with their two children last month and she didn’t know where they had gone. She filed a missing person’s report the next day on Aug. 8 and tracked his phone to Rosarito, Mexico. On Aug. 9, border officials made contact with him at the San Ysidro Port of Entry in San Diego returning to the U.S. without his children. The bodies of his children were found in Rosarito the same day.

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Matthew Taylor is seen at a hotel in Mexico with one of his children, prosecutors said. (Fiscalia General Del Estadio de Baja California)

He allegedly shot them in the chest with the spear gun.

Coleman, a QAnon and Illuminati conspiracy theorist, allegedly told investigators he believed his wife had passed "serpent DNA" onto their children and had to kill them because they were becoming "monsters."

Investigators said they recovered the murder weapon and bloody clothes where Coleman allegedly dumped them in Mexico.

"There are no words to describe the profound grief that envelops an entire community when a child is murdered," Acting U.S. Attorney Randy Grossman said in a statement Wednesday. "The Department of Justice is determined to achieve justice for these victims and their loved ones."

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Coleman had previously been charged with the same crimes in a Los Angeles federal complaint, which prosecutors intend to dismiss, the U.S. Attorney’s Office said.

He will make his first court appearance for the indictment in Los Angeles on Thursday and will later be prosecuted in San Diego.

Southern California father indicted in spear gun killings of his toddler son, baby daughter

Coleman allegedly told investigators he believed his wife had passed “serpent DNA” onto their children and had to kill them because they were becoming “monsters"