A driver has been arrested after fatally striking a woman riding a bicycle in lower Manhattan last night. And he was nabbed thanks to an off-duty MTA officer.

According to the NYPD, police responded to a call about a person hit by a car at Chambers Street and West Street around 7:52 p.m. Saturday. They say: "Upon arrival, police determined that a 2011 Ford truck being driven by a 26 year-old male was traveling southbound on West Street and making a right turn to westbound Chambers Street when he struck a female bicyclist also traveling southbound in West Street."

The victim, who suffered head and body trauma, was taken to Bellevue Hospital where she was pronounced dead.

An eyewitness told WABC 7 that the cyclist "was trying to get up—they were trying to help her. Somebody chased after [the truck driver] and they called the cops." It turns out the person chasing after the driver was off-duty MTA officer Otis Noboa.

WABC 7 reports, "Noboa says he was driving northbound on the West Side Highway, saw the victim lying on the road, and pulled over. After witnesses told him what happened, he radioed for backup, then canvassed the area. Moments later, Noboa spotted the vehicle that matched the description by witnesses just three blocks away. Noboa says the suspect had pulled over with his engine running, didn't say a word, and calmly surrendered."

Police charged NJ resident Samuel Silva, 26, with manslaughter, leaving the scene of an accident, failure to yield to a pedestrian, and driving while ability impaired.