Police released a photo of the alleged gunman involved in Thursday evening's incident. View Full Caption Chicago Police Department

CHICAGO — Police released a subway surveillance photo of the alleged gunman involved in the apparently "targeted" shooting in the Jackson Red Line station Thursday evening.

The incident started around 7:45 p.m. Thursday, and stemmed from a fight that occurred in the station between two groups, police said.

The gunman shot a 24-year-old man in an "apparent targeted attack," police said. The victim survived after being shot in his arm and ankle.

"The victim was targeted on the platform and attempting to flee from the offender by entering the train when he was shot," police said in a statement.

Police describe the suspect as a 20- to 25-year-old black man who is 5-foot-9 to 5-foot-11 tall and weighs 150 to 175 pounds.

He was wearing a dark hoodie (with his hood pulled over his head), dark pants and white shoes, while carrying a blue cinch bag.

Anyone with information can call anonymously at 312-747-8380.

Prior to spilling into the CTA station, the fight began at Pritzker Park at State and Van Buren streets, according to a witness.

About 7:45 p.m., some 50 teens and young adults began fighting in the park across from the Harold Washington Library, said the witness, a 35-year-old Bridgeport woman.

"Someone yelled, 'Someone got knocked out! Someone got knocked out!'" she said, and she saw that an injured person on the ground. She called 911.

Then, about half of the group ran to the southwest Jackson CTA subway entrance, downstairs to the ticket-purchasing platform, said the witness, who followed the group. The teens and young adults jumped over the turnstyle and ran down to the train platform, she said.

The group continued to fight on the subway platform.

When a Red Line train pulled into the station, the group ran onto a train car. Before the doors closed, four or five gunshots rang out, she said.

The panicked witness, who asked not to be named, ran from the platform back to street level on State Street and hid with other witnesses in a store.

"We ran into the first store we saw open," she said. "People were crying, 'Someone is shot down there.'"

The woman, who takes the Red Line to the Loop several times during the week for school, said the Downtown shooting below busy State Street was "shocking."

"I was shaken. This is happening in the middle of Downtown and it wasn't even dark yet," she said.