Thirty-four people were injured when an A train derailed Tuesday, the latest high-profile breakdown for a buckling subway system and its new boss. NY1's Jose Martinez filed the following report.

Passengers escaped onto the tracks after a southbound A train derailed entering the 125th Street station.

The impact shredded equipment and deepened questions about an aging system strained by crushing demand and soaring delays.

"All of a sudden, it was like a bucking horse. We were going up and down, all up the sides," said one rider.

"People are screaming, there's all this smoke, and I'm thinking, 'I got to get off this train,'" said another.

The derailment occurred at 9:45 a.m., when the brakes went into emergency and two cars skipped the tracks and careened into a wall.

"With a brake going on into emergency, we need to figure out what exactly caused that," said MTA Chairman Joe Lhota. "But this, to the best of my knowledge, does not look like a failure on the part of equipment. It does not look like a failure on the part of the track itself."

The MTA chairman said he did not know if someone pulled the emergecy brake.

The train 's operator, Chris Miller, tells NY1 he felt the train lunge forward, pull back and then lunge forward again.

"Most of the time, when a train goes into an emergency, it's usually something like a smooth kind of stop. And this was an abrupt one," Miller said.

The derailment had a cascading effect, disrupting service on A, B, C and D lines.

It overshadowed Lhota's return as MTA chairman on a day he was supposed to celebrate the return of the South Ferry station after flooding by Hurricane Sandy.

His boss, Governor Andrew Cuomo, called the derailment "an unacceprtable manifestation of the subway's current state."

"Look, one of the things I will do while I'm here is to rebuild the confidence of people in ability of the MTA," Lhota said.

The motorman, a trainee on board, and the conductor herded passengers into the first two cars, which stopped just inside the station. Those riders exited onto the platform.

"To do that by ourselves without supervision is a tough task," Miller said.

Ten riders escaped into the pitch-black tunnel, joined by others from three other trains stranded by the derailment.

It's now up to investigators to get to the root of the latest problem, all while riders and advocates say the system is near a breaking point.