Man questioned in NYC subway rider's death

View more videos at: http://nbcnewyork.com. By Shimon Prokupecz and Jonathan Dienst, NBCNewYork.com Police have a man in custody believed to be the suspect who pushed a subway rider to his death on the subway tracks at 49th Street in Manhattan after an argument. The man's name was not immediately released. He is being questioned, a law enforcement official told NBC 4 New York. He is suspected of pushing 58-year-old Ki-Suk Han off the platform at the N, Q, R station Monday afternoon. Han was hit by a southbound Q train and died. Witnesses told police the suspect was mumbling to himself before he and Han began arguing on the platform.  A bystander recorded part of the fight between the two men and turned the video over to police, who released it to the public Monday night, and received several tips. The man who allegedly pushed Han is heard cursing and saying, in substance, "Leave me alone... stand in line, wait for the R train and that's it." He then pushed Han onto the tracks, police said. Han tried to climb back up onto the platform but died after getting trapped between the train and the platform's edge.  Witness Patrick Gomez, who was in the station, says he heard a "thud that didn't sound normal" when the train pulled into the station. "People are just standing there in fear and shock, not really knowing what's going on," he said. "Some people started running out of the platform, others just stood there." Read more news on NBCNewYork.com  He says police evacuated the platform within minutes. Mark Lennihan / AP Police stand outside a New York subway station after a man was killed there on Monday. Subway pushes are unusual. Among the more high-profile was the January 1999 death of Kendra Webdale. A former mental patient admitted he shoved her to her death. Following that, the state Legislature passed Kendra's Law, which lets mental health authorities supervise patients who live outside institutions to make sure they are taking their medications and aren't a threat to safety.