Group pulls out knife, robs Brooklyn commuter at Crescent Street J train station

The NYPD is investigating overnight robbery by a group of people at the Crescent Street J train station in Brooklyn.
Police say one of the five suspects pulled out a knife and demanded money from a 28-year-old man at around 2:40 a.m. The suspects took cash and the victim's phone before running off.
It's unclear if this happened on the platform or inside a train.
The victim man was not physically injured.