An FBI affidavit says that a 3-year-old child witnessed the killing of three people on Montana's Crow Reservation and named a family member as the shooter.

Twenty-two-year-old Sheldon Bernard Chase was captured in Washington state and is due before a federal judge on Thursday to face charges that he killed his grandmother, cousin and cousin's boyfriend in their home on Tuesday.

The cousin and boyfriend had two-year-old and three-year-old sons.

Authorities and people who know Chase say he suffers from mental illness. The FBI affidavit says Chase had stopped taking his medications prior to the shootings, although it does not specify when.

The affidavit also says Chase on Monday left his mother's North Dakota house with a "Sitting Bull commemorative gun" with him. Chase asked to be returned to Montana as soon as possible to face charges.

Associated Press