Police are investigating the weekend shooting deaths of two adults and two girls in a San Francisco home as a murder, though they have not ruled out murder-suicide.

Police recovered a gun at the house where they found the four bodies Sunday morning, Lt. Judie Pursell said. Investigators said they had no leads and were not releasing the victims' names.

Property records showed Anthony and Anna Shami owned the red-tiled home with front-yard rose bushes. Neighbors said they had two daughters, ages 15 and 10.

Pursell said police believed the victims were the occupants, but were waiting for a coroner's report. She said police had no previous contact or domestic violence calls to the home.

The San Francisco Chronicle had reported Monday that there were no signs of forced entry into the house in the city's Bernal Heights district, and that police believed it was a muder-suicide.

Marlo Contreras, who lives across the street, said she heard four shots around 6 a.m. Another neighbor, Jim O'Shea, said he heard loud motorcycle noises and car alarms early Sunday before police arrived.

Anthony Shami reportedly was a member of the Hells Angels motorcycle group.

Contreras described the Shamis as quiet and friendly. She said they had lived in the middle-class neighborhood for at least four years.

The bodies were discovered at 9:45 a.m. Pursell would not say if the killings were committed by an intruder or if it was the result of a murder-suicide. She did confirm that San Francisco police had no previous contact or domestic violence calls to the home.

"It's always very tragic when anyone's murdered," Pursell said. "But when you have children involved it's quite overwhelming."

Contreras said occasionally, groups of motorcycle riders would gather outside the Shamis'  home, but neighbors said they were respectful and didn't cause problems. A black SUV with a Harley-Davidson sticker was hauled away by police as evidence.