Teen gets on bus with severed arm after robbery victim runs down assailant in SUV

CANARSIE, Brooklyn -- A suspect fleeing on foot from an armed street robbery was run down by an SUV driven by his victim in Brooklyn early Friday afternoon, severing the assailant's arm.

It was quite a turn of events for Phillip Pierre. The married father of three found himself cuffed in a police stationhouse, marched to a waiting van for a trip to court, accused of attempted murder.

"Two families are destroyed tonight - my cousin, and this kid's family," said Pierre's cousin, 'Michael'.

'Michael' said Pierre was just trying to help police catch the teen who had robbed him. Zachary Sam, 17, had arranged to meet Pierre in his Honda Pilot to buy a pair of Air Jordan 8 sneakers for $190. Police said Sam pulled out a gun and stole the sneakers instead.

Surveillance video captured Sam getting out the car and Pierre driving away, but then he made a U-turn and appeared to aim straight at Sam, mowing him down. Pierre's cousin insisted he was just trying to detain him.

Watch the video here: (WARNING: Video may be considered disturbing)

"I know what the video's showing - if somebody pulls a gun in your head, and you're trying to get the cops to catch him, what would you do? You're telling me just let him go?" he said.

Sam, who lost an arm in the crash, ran away from the scene then stumbled to his house around the corner, where he collapsed in front of his mother.

Doctors at Bellevue Hospital spent hours trying to reattach his arm, which officers found at the scene, along with his gun. When Sam is out of the hospital, he will be heading to jail.

Raymonde Jason is Sam's upstairs neighbor - he has known him since he was 6 years old.

"Should we call that instant karma? I don't know what to say. He should not have been that way. He should not have been putting himself in a situation to rob," Jason said.

Charges against Sam were pending. Pierre was charged with second-degree attempted murder.