Two unarmed volunteer police officers were shot dead outside a strip of busy restaurants and bars near New York University after they bravely followed a gunman who had killed a pizza parlor employee, the mayor said. The lethal gunman was shot and killed later by regular police officers who raced to the scene Wednesday night in downtown Manhattan, Mayor Michael Bloomberg said. "Tonight was a horrible night for the New York Police Department and for our city," he said. The bedlam began around 9 p.m., when the gunman went into a Greenwich Village pizzeria, asked for a menu and then shot an employee 15 times in the back, the mayor said. The two auxiliary officers - civilian volunteers who wear uniforms, are unarmed and help patrol streets - followed the killer briefly before he turned his gun on them. A nearby restaurant worker, Nikola Simic, said he saw police officers swarm toward the middle of the street where the auxiliary officers were slain by the gunman. "Then we heard a shooting that was like a good five minutes," Simic said. Witness Darren McNamara, a tourist from London, said he heard two bursts and thought it was someone shattering the front window of a shop, but it turned out to be gunfire. The street where the shooting occurred is located near New York University's downtown Manhattan buildings on a block populated with bars and restaurants. Police cordoned off several blocks nearby as patrons poured out of the establishment after the altercation. They escorted area residents to their homes.