Police and rescue officials aid an injured person at the scene of a rush-hour accident Friday in Chicago. Authorities said a tractor trailer, background, rammed into an elevated Chicago Transit Authority train station, killing at least two people and injuring more than a dozen others.

Chicago ? A tractor trailer that witnesses said didn’t seem to slow down rammed into a crowded bus shelter and a Chicago Transit Authority train station during the evening rush hour Friday, killing two people and injuring more than a dozen others.

The truck smashed into the street-level bus shelter without warning, then “climbed the stairs” of the station’s north stairwell around 5:20 p.m., said fire department spokesman Larry Langford.

“This is rush hour so it’s bad,” Langford said.

Those killed, both women, were apparently walking near the Cermak-Chinatown Red Line station on the city’s South Side, Fire Department spokeswoman Eve Rodriguez said. They were dead at the scene, she said.

Twenty-one people were transported to area hospitals, said fire department spokesman Larry Langford. Eleven were in critical condition, including four children, eight adults were in stable condition and two adults were in good condition.

Witnesses said the truck didn’t appear to slow down before ramming into the station’s stairwell.

Elliott Reed, 30, was walking on the street when he “heard the big bang and saw the truck go right into the station.”

Reed said the scene was “surreal,” with eyewitnesses asking each other, “Did you see what just happened?”

The intersection has a risky reputation because the traffic lights there change quickly, said Meekus Wong, who works at a restaurant located directly in front of the train station.

“That was always a very dangerous intersection because the traffic lights switch really fast,” she said.

“I was supposed to take the train. Thank God I took the bus,” she said.

“Right now this is just a tragic traffic accident,” said Chicago Police Department Deputy Chief Joseph Patterson.

The truck’s driver was treated at an area hospital and released Friday night. Police led him from the hospital in handcuffs, but he was not under arrest and had not been charged with anything as of Friday evening, police spokesman John Mirabelli said.