UPDATED 12/27/11 6:57 a.m.

CHICAGO (CBS) — Train service was back to normal Tuesday morning, after a disruption the evening before when man was shot at the busy Roosevelt Orange and Green Line station.

The shooting happened around 7 p.m. at the station, located close to the intersection of Roosevelt Road and State Street, police said.

The victim, a 21-year-old man, suffered a gunshot wound to the upper left torso and was taken to Northwestern Memorial Hospital in critical condition, authorities said.

Commuters said some people were trampled as they headed up the escalators to get to safety.

“We heard shots and screaming from up there, and then everybody just started coming towards us. So we turned around to run down because we knew that there were shots fired, and everybody was screaming and running down, and they just pushed us all down,” said commuter Judith Nieves.

CBS 2’s Derrick Young happened to be exiting a Red Line train in the Roosevelt subway station below just before the shooting happened. He said tensions had been escalating with some people on the train, and “once the train got off, everyone just got crazy. Punches started to fly.”

From that point, it got worse.

“I ran up the stairs immediately, and it was interesting how a lot of people stood there and watched, and it’s one of the worst things you can do is watch a situation, and so the shots obviously happened after that, because I was gone fairly soon, but you could tell that it was not going to be a situation,” he said.

Young said the fight likely migrated from the subway station up to the ‘L’ station.

Following the shooting, power was shut off on the elevated tracks for the Orange/Green Line trains for about 20 minutes, Chicago Transit Authority spokesman Brian Steele said.

Police have interviewed several people in connection with the shooting, but no one was in custody as of early Tuesday.

The Sun-Times Media Wire contributed to this report.

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