AMERICAN FORK, Utah -- A 5-month-old boy is dead in what police allege was a murder-suicide attempt.

The shooting happened at a home near 500 North and 500 East about 1 p.m. Friday, police said. Officers were called to the home and found a 5-month-old boy who had been shot in the head with a rifle.

The infant was taken by ambulance to a local hospital, then flown to Primary Children's Medical Center in Salt Lake City where he was pronounced dead.

Police said Joshua Petersen, 21, was arrested for the shooting of his son, Ryker.

"Through our investigation we learned Joshua's intent was to kill his son and then in turn, kill himself. But he did not do that," American Fork Police Sgt. Gregg Ludlow said Friday.

He was about to shoot himself when a family member intervened, Ludlow said.

Police refused to divulge a motive for the slaying. Ludlow said Petersen lived at the home with family members, but they would not reveal any further details. Neighbors told FOX 13 an older couple lived at the home with adult children and grandchildren.

"It is just horrifying to me. I can't understand it," said Fran Keller. "To find out that somebody didn't cherish their 5-month-old like I cherish mine. It's horrendous! I can't understand how anybody could take the time to go get a gun to hurt a child."

Petersen was being held in the Utah County Jail without bail pending an appearance before a judge. He was booked on suspicion of aggravated murder, a first-degree felony.