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After he allegedly shot and killed his mother and brother last month, a 25-year-old Utah man asked another man to "help him hide two bodies," according to a newly unsealed search warrant affidavit.

Seth Gordon Peterson is charged in 7th District Court with two counts of aggravated murder, accused of killing 45-year-old Susan Peterson and 23-year-old James Peterson. The defendant is also charged with attempted aggravated murder, aggravated robbery and failure to stop at the command of police.

On Nov. 2, Seth Peterson's uncle saw his nephew point a rifle at Susan Peterson and heard a shot, he told police, according to the affidavit. After the shot was fired and Susan Peterson fell to the ground, the uncle said he heard Seth Peterson say, "I just shot my mom in the f—-ing face," the affidavit states.

Shortly after that shooting, the uncle said he saw James Peterson drive towards his mother's body. Another gunshot was heard, the uncle told police, and he then saw Seth Peterson drive away in the truck that James Peterson had driven there, the affidavit states.

The truck owner told police that after the shootings, Seth Peterson drove up to him and said, "You have to help me hide two bodies," and pointed a rifle at his chest.

The truck owner pulled the rifle away, according to the affidavit, and Seth Peterson then got a crow bar and began hitting the other man with it. The assault continued until Seth Peterson got into the truck and left.

Deputies were called after someone called 911 reporting shots fired and spotted Seth Peterson driving away from a farm about 7 miles west of Price, just off State Road 122.

Police caught up to the truck, according to the affidavit, and Seth Peterson led them on a lengthy pursuit that ended after he crashed the vehicle.

Officials have not revealed a motive for the killings.

The defendant, who is being held without bail at the Carbon County jail, is due in court on Jan. 3, where he is expected to decide whether he wants a preliminary hearing.

Twitter: @jm_miller