NEW YORK - A gunman with a fake beard and carrying 100 rounds of ammunition fatally shot a pizzeria employee and two unarmed volunteer police officers in a trendy Manhattan neighborhood before other officers shot him to death, the mayor said Thursday.

A policeman looks at the body of the unidentified gunman in the street in New York's Greenwich Village section Wednesday night March 14, 2007. [AP]

Authorities were still investigating why David Gavin, 32, went into a Greenwich Village pizzeria around 9 p.m. Wednesday, asked for a menu and then shot an employee 15 times in the back before fleeing, Mayor Michael Bloomberg said.

Nicholas Todd Pekearo and Eugene Marshalik, two of the city's nearly 4,500 auxiliary police officers, responded to the shooting and approached Gavin, who crossed the street and fired at them. Auxiliary officers are civilian volunteers who wear uniforms, are unarmed and help patrol streets.

Gavin then exchanged gunfire with uniformed officers, the mayor said. Several uniformed officers suffered minor injuries.

Authorities recovered the 9mm semiautomatic pistol Gavin fired, plus a .380-caliber semiautomatic handgun in a bag with the ammunition, Police Commissioner Raymond Kelly said. Gavin shot at least 23 rounds.

"He appeared to be ready to take even more lives," Kelly said.

A worker in a nearby restaurant, Nikola Simic, said he saw police officers swarm toward the middle of the street where the auxiliary officers were slain.

"Then we heard a shooting that was like a good five minutes," Simic said.

Police identified the employee as Alfredo Romaro, 35.

Pekearo, 28, was a writer with a book scheduled to be published soon, the mayor said. Marshalik, 19, a student at nearby New York University, had immigrated from Russia, Bloomberg said. The mayor said Marshalik hoped eventually to join the police force.

"Tonight was a horrible night for the New York Police Department and for our city," Bloomberg said. "Two men who volunteered their time to make our city the safest big city in America lost their lives helping to keep it exactly that way."

Marshalik and Pekearo were the first New York City auxiliary police officers to die in the line of duty since 1993, according to the mayor. Only five other auxiliary officers have died in the line of duty in the city's history.

The street where the shooting occurred is located near NYU's downtown campus, close to Washington Square Park and near several famous bars and restaurants, including Cafe Wha?, where Bob Dylan used to perform.