NEW TOWN, ND—A twelve-year-old born on the Fort Berthold Reservation in North Dakota survived a deadly shooting by faking his death as he lay under his slain brother’s body. Christian Schuster told the Rev. Grant Patterson that “he laid there and played dead until the shooter left the house.”

The pastor of the Bethel Lutheran Church in New Town said that he spoke with Christian about an hour after the killings.

Also killed in the shootings were his grandmother and three of his siblings. Martha Johnson, 64, and three of her grandchildren—Benjamin Schuster,13, Julia Schuster, 10, a...