PITTSBURGH â 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. When officers Paul Sciullo III and Stephen Mayhle arrived, Margaret Poplawski opened the door and told them to come in and take her 23-year-old son, apparently unaware he was standing behind her with a rifle, the affidavit said. Hearing gunshots, she spun around to see her son with the gun and ran to the basement. "What the hell have you done?" she shouted. The mother told police her son had been stockpiling guns and ammunition "because he believed that as a result of economic collapse, the police were no longer able to protect society," the affidavit said. Friends have said Poplawski was concerned about his weapons being seized during Barack Obama's presidency, and friends said he owned several handguns and an AK-47 assault rifle. Police have not said, specifically, what weapons were used to kill the officers. Autopsies show Sciullo, 37, died of wounds to the head and torso. Mayhle, 29, was shot in the head. A witness awakened by two gunshots told investigators of seeing the gunman standing in the home's front doorway and firing two to three shots into one officer who was already down. Sciullo was later found dead in the home's living room, and Mayhle near the front stoop, police said. A third officer, Eric Kelly, 41, was killed as he arrived to assist the first two officers. Kelly was in uniform but on his way home when he responded and was gunned down in the street. Kelly's radio call for help summoned other officers, including a SWAT team. The ensuing standoff included a gun battle in which police say Richard Poplawski tried to kill other officers. Poplawski is charged with three counts of criminal homicide and nine counts of attempted homicide _ one each for the eight officers who were shot at in an armored SWAT vehicle, plus a ninth who was shot in the hand as he tried to help Kelly. Poplawski also was charged with possessing an instrument of crime: the bulletproof vest he wore during the gun battle. The criminal complaint doesn't say how Poplawski obtained the vest. Police Chief Nate Harper Jr. has said the vest kept Poplawski from being more seriously wounded, but police have not specifically said how many shots were stopped by the vest. A district judge arraigned Poplawski at UPMC Presbyterian Hospital, an arraignment court worker told The Associated Press on Sunday. Poplawski was being treated there for gunshot wounds to his extremities and remains under guard. Police and hospital officials have not released his condition, though he is expected to survive. It was not immediately clear if Poplawski has an attorney. A preliminary hearing, at which Poplawski could challenge the charges, wasn't immediately scheduled. Poplawski is also charged with firing weapons into two occupied neighboring homes and with recklessly endangering four people, two in each home, with gunfire. No civilians were wounded. Police did not immediately say why Poplawski fired toward the homes, but some officers were seen going into nearby homes and perching on rooftops. Police did not immediately release any information on funeral arrangements for the officers, though a memorial was held Saturday night outside the police station where all three slain officers worked. Bagpipers played near a black wreath hung outside the station and an Allegheny County 911 dispatcher did a roll call for the 11 p.m. shift change. Various officers responded when their car numbers were called, but there was silence when the names, unit numbers and badge numbers of the slain officers were called out. Chief Harper radioed back in each instance that the officer had been killed in the line of duty as hundreds of officers and other mourners stood listening nearby.