Pittsburgh ? A 911 call that brought two police officers to a home where they were ambushed, and where a third was also later killed during a four-hour siege, was precipitated by a fight between the gunman and his mother over a dog urinating in the house.

The Saturday argument between Margaret and Richard Poplawski escalated to the point that she threatened to kick him out and she called police to do it, according to a 12-page criminal complaint and affidavit filed late Saturday.

Autopsies show officer Paul Sciullo II died of wounds to the head and torso. Officer Stephen Mayhle was shot in the head.

A third officer, Eric Kelly, 41, was killed as he arrived to assist the first two officers.