Police say a man is in critical condition after getting shot by a Metropolitan Transportation Authority employee Tuesday night at the 4th Avenue subway station.

According to the NYPD, two MTA employees, one armed and the other was not, were waiting on the southbound R train platform when a man walked up to them and started threatening and harassing them.

Authorities say the 39-year-old male suspect followed the two MTA employees onto the train. They tried to get away from the suspect by getting off on Union Street, but the man followed them. That’s when the armed MTA employee tried to calm the suspect down, but he was not cooperating.

The armed MTA employee pulled out his firearm, telling the suspect to back up. That's when the suspect tried to forcibly remove the firearm and a gunshot was fired off into the suspect's chest.

The victim is in critical condition.

Moments before that shot was fired, one of the employees was trying to fix the Metro card machine while the armed employee was acting as security. The MTA employee who fired the gunshot is a 21-year veteran and is one of the 274 armed collection agents working for the MTA.

Police say there is surveillance video of the entire incident. The MTA is cooperating with the investigation.