A man who stopped by his newly purchased Southern California home expecting to find its previous owners packing up instead stumbled on one of them dead in a bedroom.

Mary Karacas, 75, was arrested Sunday on suspicion of killing her 83-year-old live-in boyfriend, Salvatore Orefice, Simi Valley police said. Karacas told detectives that she shot him after they argued.

The man who bought the house from the couple 30 days earlier found Orefice's body after going to check on their progress moving out.

"When he knocked and there was no response, he found an open door and thought it was suspicious, so he went in," police Cmdr. Roy Jones said.

The new homeowner found Orefice's body under a blanket on a bed and called authorities. The blanket covering the body indicated that the shooting likely was not self-inflicted, Jones said.

Police say it is not clear when Karacas shot her boyfriend and how long he had been lying in their house before being found. She was not at the property when the homeowner stopped by.

Authorities found the gun after she told investigators it was in her car.

Karacas was booked into jail Monday on a felony murder charge, with bail set at $750,000. Her next court hearing is set for Aug. 3.

It was not clear whether she had an attorney. She has no prior record other than traffic violations, police said.