The Toronto Transit Commission has suspended one of its streetcar drivers after he tried to chase down a man who had allegedly sexually assaulted one of his passengers.

Police say the assault happened Wednesday afternoon on the busy 501 Queen Street streetcar, near John Street.

A passenger alerted the driver to the assault who stopped the streetcar.

But before police could arrive the suspect took off down Queen Street and the alleged victim ran after him.

The streetcar driver then chased after both of them — leaving a streetcar full of passengers sitting idle.

The TTC says that was the wrong thing to do.

TTC drivers are not allowed to leave their vehicle unsecured — and under no circumstances should they put themselves, or their passengers in danger.

A spokesman for the TTC confirmed to CBC News that the driver was relieved of duty and that a disciplinary hearing has been ordered. Depending on the driver's record and the circumstances surrounding the event the driver could lose his job.

The union says instead of being relieved of duty and facing disciplinary action the driver should be praised.

"I think he should be recognized and commended," said union president Bob Kinnear.  "It's unfortunate that the TTC is taking action."

Kinnear says the driver, whose name has not been released, "was concerned for the victim ... he was looking out for one of our passengers that had been criminally assaulted."

Passengers told about the TTC's action were furious. 

"I think that's absolutely ridiculous. The man saw something happening that shouldn't happen and did his duty, like anyone would in that situation, to help this poor woman," said one woman.