BEACHWOOD, Ohio (AP) — Police are trying to determine a motive in an Ohio doctor's slaying that was followed by his two sons killing themselves during a standoff with SWAT officers.

Beachwood Police Chief Gary Haba said Tuesday police believe Dr. Richard Warn was killed last week by one or both of his sons. Haba says investigators and the SWAT team went to a home Friday in nearby South Euclid to gather evidence in the 59-year-old doctor's slaying.

Thirty-one-year-old Michael Warn and 29-year-old Mark Warn were found dead from self-inflicted gunshot wounds Saturday after a 12-hour standoff at a home their father purchased. Police say the standoff began with someone inside firing high-powered rifle rounds at a SWAT vehicle.

Haba says the brothers had no criminal history and investigators haven't confirmed any mental illnesses.