BOSTON -- A man whose arm was trapped by the doors on an Orange line Massachusetts Bay Transportation Authority train Monday is telling a story of panicked passengers and fear that the train would move on with his arm hanging outside.

In an e-mail to TheBostonChannel.com, Juan Sierra detailed his first-person account of doors that closed without warning as he was getting off at the State Street station.

"The doors closed right on my right shoulder as I had not had the chance to fully exit the train. The closing of the doors also sandwiched my head to the point that my glasses popped off to the outside of the train car onto the platform," Sierra wrote.

Sierra said that he expected the doors to reopen. "I was shocked, but realized that the doors sometimes try to close, but due to obstructions, reopen right away. I waited a moment. Ten seconds passed by. Here’s me hanging on to my briefcase and laptop outside the train car while I remained on the inside trying to pry the doors open."

Sierra's concern grew as he heard the brakes releasing and "one person behind me said in disbelief 'they're not really going to go, are they?'" Sierra was able to pull his arm back in before the train started to move.

When the train arrived at Downtown Crossing, Sierra said passenger concern began to grow. "A woman behind me was starting to panic, wanting to get off the train immediately I know there were people banging on doors shouting that they had not been able to get off."

After an MBTA employee saw the passengers banging on the doors, he was able to enter the train and order passengers off.

Sierra's briefcase and laptop had been picked up by a man on the platform at State Street who said he would meet him at the Back Bay station. "You will be glad to know that he came up to me (at Back Bay), with my briefcase, just as he said he would," he said.

MBTA officials said they are investigating "multiple door failures" on the train, which was taken out of service.

Sierra said he will assist in their investigation.