Spengler spent 17 years in prison for beating his paternal grandmother to death with a hammer in 1980. He had been released from parole on the manslaughter conviction in 2006, and authorities said they had had no encounters with him since.
Police Chief Gerald Pickering said investigators believe Spengler used the rifle to attack the firefighters because of the distance involved. He said police may never know Spengler's motive.
Chiapperini, who also was a police lieutenant, was driving a pumper with Scardino on board when bullets blasted the windshield. He and Kaczowka died at the scene. Hofstetter was hit in the pelvis, and Scardino was hit in the shoulder and knee.
A passing off-duty officer from the town of Greece was treated for shrapnel wounds from gunfire that hit his car.
Hearses carrying the coffins of Chiapperini and Kaczowka were escorted to West Webster Fire Station 1, where they were met by emergency vehicles with their lights flashing in salute.
Calling hours for the two men will be at Webster Schroeder High School on Friday and Saturday. A funeral for Chiapperini is scheduled for Sunday at the school, with burial in West Webster Cemetery.
A funeral Mass for Kaczowka, who worked as a Monroe County emergency dispatcher, will be held Monday in Rochester at St. Stanislaus Church, with burial at Holy Sepulchre Cemetery.