US News

SCREW-LOOSE COP STABBER

Cops shot a psycho panhandler on a crowded Brooklyn subway platform after he asked a plainclothes officer for a cigarette and then tried to stab him in the chest with a screwdriver, police sources said.

The bizarre, bloody incident began at 3:44 p.m. on the southbound 3/4-train platform at the Utica Avenue station in Crown Heights, when Stephen McKenzie, 32, approached two undercover cops and tried to bum a smoke from one of them.

The 26-year-old officer flashed his badge and identified himself.

Moments later, the crazed smoker pulled out the 6-inch screwdriver and tried to plunge it into the cop’s chest near his shoulder, the sources said.

“The cop thought he was punched initially,” a source said. “His [bulletproof] vest probably saved his life.”

The officer suffered minor stab wounds to his left shoulder and thigh in the ensuing struggle.

His partner used his baton to try to subdue McKenzie, who then allegedly tried to grab his gun. The partner then began to fight with McKenzie, and both fell to the ground. The gun discharged twice.

“Everyone on the platform just panicked and ran for the exits,” Shianna Rogerson, 19, said. “I just kept moving as fast as I could.”

The wounded cop then opened fire. McKenzie was hit three times in the chest and once in the hip. He was critically injured. The wounded cop and a 17-year-old bystander who was grazed in the leg were in stable condition at local hospitals.

john.doyle@nypost.com