CHICAGO (CBS)–A gunman wearing a surgical mask opened fire in the CTA Blue Line tunnel at Jackson Thursday around 5:05 p.m. during evening rush hour.

(WBBM Radio)

An unknown gunman wearing a surgical mask opened fire in the tunnel, firing two shots, police said during a press conference Thursday evening. One person in his 20’s was shot in the side and was taken to Northwestern Memorial Hospital in stable condition. Police said he is not cooperating with the investigation.

“But we have some pictures of him,” CPD Patrol Chief Fred Waller said. “We have some cooperating witnesses also. But the victim is being very uncooperative. He’s not cooperating with us at all.”

Police believe the shooting was targeted, and the shooter likely knew his victim.

“This area is probably one of the safest areas in the city. This is a targeted incident, so the rider should not feel any kind of discomfort,” Waller said.

Police said the gunman fled westbound through the tunnel after the shooting, possibly getting on another train. The shooter has not been located, but the gunman was caught on high resolution cameras in the transfer tunnel area. Police also found two bullet casings in the transfer tunnel.

Blue Line service was temporarily suspended between Grand and UIC-Halsted. At 5:47 p.m., the CTA announced service was resuming.

The tunnel between the Red and Blue Lines was closed for about an hour.

Traffic was shut down between Congress and State and Van Buren and State following the shooting. Lane closures have since reopened.

The suspect is about 5 feet 7 inches tall and was wearing a blue hoodie and black jeans, police said.