PITTSBURGH - AN EMERGENCY call that brought two police officers to a home where they were ambushed, and where a third was also killed later 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.

CHARGED FOR HOMICIDE 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 armoured police vehicle, plus a ninth who was shot in the hand as he tried to help Mr Kelly. Poplawski also was charged with possessing an instrument of crime: the bulletproof vest he wore during the gun battle. The criminal complaint does not say how Poplawski obtained the vest. ... more FEARS ABOUT GUN BAN Poplawski had feared 'the Obama gun ban that's on the way' and 'didn't like our rights being infringed upon,' said Edward Perkovic, his best friend. Mr Perkovic, 22, said he got a call at work from him in which he said, 'Eddie, I am going to die today. ...Tell your family I love them and I love you.' Mr Perkovic said: 'I heard gunshots and he hung up. ... He sounded like he was in pain, like he got shot.' ... more A STRING OF SHOOTINGS A string of shootings in the US in the last month alone has claimed the lives of 53 people: -MARCH 10, SAMSON, Alabama - A gunman kills 10 people and commits suicide in a rampage that spanned two dozen miles (39 kilometres) across the southern Alabama countryside. Police say Michael McLendon had struggled to keep a job and left behind lists of employers and co-workers he believed had wronged him. ... more

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 Mr Sciullo, 37, died of wounds to the head and torso. Mr 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. Mr Sciullo was later found dead in the home's living room, and Mr Mayhle near the front stoop, police said.

A third officer, Eric Kelly, 41, was killed as he arrived to assist the first two officers. Mr Kelly was in uniform but on his way home when he responded and was gunned down in the street.

Mr Kelly's radio call for help summoned other officers, including a police commando team. The ensuing standoff included a gun battle in which police say Richard Poplawski tried to kill other officers.

Saturday's slayings occurred just two weeks after four police officers were fatally shot in Oakland, California, in the deadliest day for US law enforcement since the Sept. 11, 2001, terrorist attacks. -- AP