CHICAGO (CBS) — A man was shot on a Blue Line train at the UIC-Halsted stop Wednesday morning, in an apparent robbery following an argument on the train, police said.

Police Chief of Patrol Fred Waller said a 30-year-old man was shot in the back around 10:45 a.m. as he was exiting a westbound Blue Line train at the UIC-Halsted station at 430 S. Halsted St.

“These subjects were on that train together. They appeared to have some conversation. As the victim was about to exit the train, the offender pulled on his backpack, and in an exchange of words, when the victim attempted to pull away from that offender, he was shot in the back,” Waller said.

The gunman then grabbed the victim’s backpack and ran down the platform and out of the station.

The victim was taken to Stroger Hospital in “very serious condition,” according to Waller.

Police said it’s unclear if the shooter and the victim knew each other.

“It appears to be robbery-related at this time,” Waller said.

Detectives were questioning several witnesses on the train, and have obtained photos and surveillance video of the shooter.

“At some point, we’re going to put it out, and we hope to identify him very soon,” Waller said.

Anyone who recognizes the shooter can send an anonymous tip to cpdtip.com.

Kenneth Franklin, president of Amalgamated Transit Union Local 308, which represents CTA rail workers, said violent crime is becoming too common on the transit system.

“We are genuinely concerned about the passengers. We’re genuinely concerned about our employees, and my union members,” he said. “We’re just hoping that the Chicago Transit Authority, CPD, the mayor’s office is ready to put forth a stronger effort in preventing these type of incidents.”

Franklin said he would like to see either police officers posted on CTA trains, or to have the CTA return to the days of conductors working on board trains, in addition to the train operators, to act as a deterrent against crime.

“Our members have been attacked, and they have been put in the put in the position they have to defend themselves. So they’re very concerned about their safety,” he said.

Waller said the shooting appeared to be a targeted attack, not a random act of violence.

“We have people who ride this train repeatedly, this Blue Line train, as we do the Red Line and other lines; and we do try to do the best that we can,” Waller said.

The CTA said Blue Line trains were temporarily halted after the shooting.

Trains were running again shortly before 11 a.m., but were bypassing the UIC-Halsted stop as police investigate the shooting.

As CBS 2’s Jim Williams reported, this incident happened on a train in a busy area that is home to the University of Illinois at Chicago campus. It is also just the latest high-profile crime on the Chicago Transit Authority system.

On Monday, a street musician was stabbed at the Jackson station on the Red Line downtown.

In January, neighbors gathered at the Town Hall (19th) District police station, at 850 W. Addison St. in Lakeview, to demand answers.

“I’ll tell you something – I’m mad as hell,” one man said at that meeting.

It just so happens that the increase in crimes on the CTA has been dramatic over the past few years. There were 2,737 crimes reported in 2016, 3,495 in 2017, 4,388 in 2018, and 4,497 last year.

“We’re just hoping that the Chicago Transit Authority, CPD, the Mayor’s office is ready to put forth a stronger effort in preventing these types of incidents, because they’re becoming too common,” Franklin said.

Police have added more officers to the Public Transit Unit.

Now they’re after the assailant, who was last seen running west from the Halsted Station. He stands out in a checkered hat, bright red hoodie, and red shoes.