Police in New York state say a man who killed two firefighters in a Christmas Eve ambush had served 17 years for manslaughter in the death of his grandmother.

Webster Police Chief Gerald Pickering says 62-year-old William Spengler was found dead of a self-inflicted gunshot to the head.

Police say he set fire to a car and house to lure firefighters to his house on the shore of Lake Ontario early Monday.

When firefighters arrived, he opened fire, probably with a rifle. Two firefighters died at the scene and two others were hospitalized. A fifth first responder was injured.

Police don't know a motive yet.