A 66-year-old Roslindale man is under arrest after he allegedly committed a lewd act in the men’s room at Back Bay station Thursday. 

According to MBTA Police, an officer was approached by a man who said he was using the bathroom just before 2:30 p.m., when another man exposed his genitals and began the act. 

The victim provided a description to officers, who later found a man, Neville Pinnock, matching the description and still in the bathroom. He was taken into custody and later positively identified by the victim, police said. 

Pinnock faces a charge of open and gross lewdness and is expected to be arraigned Friday in Boston Municipal Court.