BROWNSVILLE, Brooklyn (WABC) -- An off-duty MTA employee was grazed in the arm by a stray bullet while on board a subway train in Brooklyn Tuesday night.The shooting occurred just after 6:30 p.m. on a southbound 3 train at the Sutter Avenue Rutland Road station in Brownsville.Police say two groups aboard the train began fighting, and a teenager pulled out a gun and fired at least one shot."One of the groups exited the train and displayed a gun and fired into the train, striking the victim, at this time an unintended target," said NYPD Chief of Investigations for Brooklyn North Michael Kemper.The bullet grazed the 47-year-old MTA supervisor in the arm. He was taken to Kings County Hospital in stable condition. Police say he had just left work and was on the way home.A token booth clerk alerted police to the shooting by activating the emergency communications system.Three people of interest are in custody who may have been involved in the initial fight, according to police. But the shooter remains at large.Investigators are looking into whether the incident was gang-related.Southbound 3 subway trains bypassed Sutter Avenue because of the police investigation.MTA Chairman Joe Lhota and MTA President Andy Byford visited the supervisor at the hospital."This is a horrible incident and we're all pulling for a speedy recovery," said Lhota. "Transit workers are on the front lines of moving millions of New Yorkers every day and this shouldn't happen to anyone. "----------