SALT LAKE CITY — A Fairview man charged with killing his stepfather said he just decided to “do it” on Monday, according to police.

After Michael Hartnell, 32, shot and killed Joseph Vallejos, 73, in the victim’s home in the Hideaway Valley area of Fairview, Sanpete County, Hartnell took Vallejos’ cellphone and car, drove to the fire station in Indianola, called 911, and then returned to Vallejos’ home to wait for police to arrive, according to a police affidavit filed in court.

Hartnell was charged Tuesday in 6th District Court with murder, a first-degree felony, and possession of a firearm by a restricted person, a third-degree felony. Additional details about the shooting were released on Wednesday.

Sanpete County dispatchers received the 911 call about 5:20 p.m. Monday.

“Hartnell stated he shot someone and he was calling to give himself up. No information was obtained from Hartnell at the time of where the alleged incident took place,” the affidavit states.

Deputies learned the phone used to call 911 was registered to Vallejos and went to his address. There, they found Hartnell and took him into custody and also found Vallejos dead of a gunshot wound in the living room, according to the court documents.

After he was taken into custody, Hartnell was interviewed by sheriff’s detectives.

“During the interview, Hartnell told me that he did not have a good relationship with Vallejos. Hartnell described Vallejos a stepfather. Hartnell told me that he stayed at the Hideaway Valley residence with Vallejos, but that Vallejos would come and go,” the affidavit states.

Hartnell said he stole a gun out of Vallejos’ vehicle a couple of weeks ago. On Monday, he left the residence to fill up some jugs with water. When he got back, Vallejos — who had not been there earlier — had returned to the home, according to the affidavit.

“Hartnell stated that he decided to ‘do it’ ... he grabbed the pistol out of the center console of the truck and cocked it. Hartnell then walked into the house and found Vallejos in the house. Hartnell stated that he shot Vallejos in the head and he fell on the ground,” the affidavit states.

He also told investigators that he is mentally ill and “has schizophrenic episodes,” according to the affidavit.