(CNN) An Arizona man forced hot water down a 6-year-old boy's throat in an attempt to "cast the demon out" Thursday, police said in a criminal complaint.

Pablo Martinez, 31, who lives on the Pascua Yaqui Indian Reservation near Tucson, was arrested on a federal charge of first degree murder, according to a statement from a spokeswoman for the FBI office in Phoenix. The child's adopted mother is a member of the Pascua Yaqui Indian Tribe, but Martinez is not.

CNN has not been able to reach Pablo Martinez, his defense attorney or any members of his family.

Martinez told police he noticed a demon inside the 6-year-old within the last week, the complaint said.

He volunteered to give the boy a bath Thursday, he and the child's adoptive mother, Romelia Martinez, told police.

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