Locked emergency doors trapped straphangers inside the subway car where a crazed gunman set off gas canisters and and fired off dozens of rounds Tuesday morning.

Footage and witness accounts from the scene reveal a terrifying few minutes as riders scrambled through a cloud of smoke as gunshots rang out, unable to move between cars to get to safety.

A brave 20-year-old man, Fitim Gjeloshi, tried to break down the locked doors after one of the shooter’s bullets passed through his right pant leg, narrowly missing his groin.

“I jumped over the seats at the back of the train, climbing on top of people. I kicked the handle of the first door and opened it,” Gjeloshi recalled Wednesday.

As Gjeloshi moved out of the train’s second car where the shots were fired, the emergency door at the rear of the train’s front car was also locked — and he was unable to get it open.

“I was banging the door and people were looking at me,” he said. “People piled up behind me, fainting as he shot down their legs.”

Gjeloshi said he was stuck between the cars until the train got to the 36th St. station, where the gunman fled. He helped get injured riders across the platform on to an R train, which took them to the 25th St. station. There, EMS workers came to their aid.

On most New York City subway cars, the doors at either end are unlocked — and transit rules only allow riders to pass through them during emergencies. But on the 45-year-old type of train car where the attack took place, the doors have been locked shut for decades.

Those older cars — called R46s — are 75 feet long, 15 feet longer than newer models that the Metropolitan Transportation Authority has bought over the past 20 years.

“The longer cars, when going around turns or curves, swing out more than the shorter cars, and a person attempting to walk between cars could more easily fall,” said a train operator who’s driven the R46s, which run on the A, C, N, Q and W lines.

It’s the same case on the MTA’s 35-year-old R68 subway cars, which are assigned to the B, D, N, Q and W lines.

The MTA takes the risk of people falling between those older subway cars so seriously that crews are required to keep them locked whenever they’re in service.

When one of the emergency doors is open or unlocked, a blue indicator light on the trains’ exteriors activates. When that happens, subway crews are required to call the subway’s rail control center and go investigate the door, according to an MTA policy reviewed by the Daily News.

MTA Chairman Janno Lieber said on WCBS 880 radio Wednesday morning that the agency will “reexamine” the locked door policy.

“Many of us grew up in New York where you could move between the cars,” said Lieber. “The problem with that is a lot of people were dying because they slipped as they moved between the cars.”

Lieber also pointed out the MTA is awaiting the delivery of new subway trains that are interconnected and have no doors between cars. Those types of cars are used in transit systems in cities including Paris and London.

The MTA ordered 20 of them to test on the subway, which are scheduled to be delivered in June.