The robbery suspect was at the Manhattan-bound M train near the Northern Boulevard station in Woodside at around 8 a.m., according to authorities and MTA officials.
Subway service was suspended for nearly an hour as police investigated the incident from the 65th St. station between the boroughs on the E, F, M, and R lines.
The alleged thief punched a good Samaritan who tried to stopped the mugger from robbing the boy, authorities said.
Once the train stopped at Northern Blvd., the mugger ran out of the train and onto the track bed in an attempt to escape, according to the New York Daily News.
The robbery suspect made it to the express track, when he was hit by an oncoming train, police said. He appeared to have minor injuries: only bruises and scratches.
The mugger, the samaritan who tried to stop the robbery, and a woman who also tried to intervene were all taken to Elmhurst Hospital for treatment, the Daily News reported.
According to NBC 4 News, the suspect is expected to be charged with assault, possession of stolen property, and criminal trespassing.
Commuters were provided shuttle-buses to other train stations to get to their destinations, according to an MTA bulletin.
Here are some photos of the mayhem at a crowded train station earlier this morning: