PITTSBURGH — A man being tried on charges he murdered three city police officers who responded to a domestic disturbance call was a “coward” who fired extra shots just to make sure the officers were dead, a prosecutor told the jury in opening statements Monday.

Allegheny County Deputy District Attorney Mark Tranquilli spoke for about 30 minutes to open what’s expected to be a two-week trial before a sequestered jury.

The jury, bused to Pittsburgh on Sunday, was selected earlier this month more than 150 miles away in Harrisburg to avoid any prejudice because of pretrial publicity surrounding Richard Poplawski, 24. He has pleaded not guilty.

Poplawski’s mother woke him early on the morning of April 4, 2009, upset because he had failed to let some puppies out of the house before they urinated. When the argument escalated, Margaret Poplawski called 911, and while she mentioned her son had weapons, she told the dispatcher they were legal and not “in play” in the dispute, Tranquilli said.

Poplawski donned a ballistic vest and readied three weapons — a 12-gauge shotgun loaded with pellet- and rifled-slug shells, a .357 Magnum and an AK-47 assault rifle, Tranquilli said.

When Officer Paul Sciullo II arrived at what police believed was a routine disturbance call, Poplawski killed him with the shotgun, then engaged in a gun battle with a second officer, Stephen Mayhle, who was “outgunned” with only his .40-caliber Glock pistol, Tranquilli said.

The third officer killed, Eric Kelly, had arrived home — about two blocks from Poplawski’s residence — after an overnight shift but went to back up the others when he heard radio calls about the shootings, Tranquilli said.

“He never even got out of his SUV. Richard Poplawski was waiting for him on the high ground,” Tranquilli said, noting how Poplawski fired on the officers, and at least nine others who responded to the shooting, from his house.

Poplawski faces three umbrella counts of criminal homicide, and could face the death penalty if the jury decides any or all the shootings rise to first-degree murder.

He’s also charged with nine counts each of attempted murder and assault on law officers for shooting at other police, as well as lesser charges, prosecutors said.