AZUSA, Calif. — A gunman with a high-powered rifle was found dead inside a home in a suburb of Los Angeles on Tuesday after shooting at police officers who responded to a report of gunfire and found one person fatally shot and two others critically injured, the authorities said.

It was not clear if the gunman — a man whose identity was not immediately known — died of a self-inflicted gunshot wound or had been shot by the police, Lt. John Corina of the Los Angeles County Sheriff’s Department said at a news conference.

“We’re in the process of trying to figure out why this happened and who this person is and what exactly made him snap,” he said.

The victim who was fatally shot was a man, but no details were immediately available about him. The two other victims, women ages 65 and 59, were in “really critical” condition, Lieutenant Corina said. “We don’t know what’s going to happen to them,” he said.