New York City Police officers are searching for a gunman after a subway passenger was shot and killed in what investigators describe as an unprovoked attack.

The suspect was pacing back and forth in the last car of a Manhattan-bound Q train as it crossed over the Manhattan Bridge around 11:45 a.m. Sunday when he pulled out a gun and “without provocation” fired it at a 48-year-old passenger at close range, striking him in the chest, witnesses told investigators, NYPD Chief of Department Kenneth Corey announced at a press conference.

When the train pulled into the Canal Street station — the first Manhattan stop on the Q line — the suspect fled, Corey said, describing him as dark-skinned with a beard and “heavy-set” and last seen wearing a dark-colored sweatshirt, gray sweatpants and white sneakers. He is still at large.

Emergency responders attended to the victim at the scene, Corey said. He was transported to Bellevue Hospital, where he later died. The NYPD identified the victim as Daniel Enriquez.

No others were injured in the shooting, Corey said.

Preliminary information suggests there was no prior contact between the victim and suspect, Corey said.

Witnesses who may have photos or video of that altercation are asked to share them with investigators.

Enriquez’s sister, Griselda Vile, told ABC News he…