A stabbing attack on the Chicago Transit Authority (CTA) Red Line early Friday morning left four people injured.
The incident occurred shortly after 2 a.m. CT, and the CTA tweeted Friday morning that Red Line trains were running but bypassing the North-Clybourn station due to an ongoing investigation by the Chicago Police Department.
"Shuttle bus available Fullerton to Clark/Division," it explained.
Police told Fox News that the victim was a 42-year-old male who exited the Red Line train at the 1500 block of North Clybourn and switched to another train car.
A group of six offenders proceeded to follow the victim onto the train, with the intention of robbing him.
The group began to attack and batter the man with a knife and a broken glass bottle.
The victim produced his own knife as he sustained several stab wounds and lacerations. He was transported to Northwestern Hospital in serious condition.
Three of the assailants sustained injuries during the assault.
A 52-year-old male who was stabbed in the neck was transported to Stroger Hospital in serious condition.
A 36-year-old male who sustained lacerations to the forearm was also transported to Stroger Hospital in fair condition. A 24-year-old who had been stabbed in the back was transported to Northwestern Hospital, where his condition was stabilized.
All six offenders were placed into custody.
"This kind of violence is absolutely unacceptable, and we applaud the Chicago Police Department for its quick actions to arrest the suspects. CTA will continue to assist CPD in its investigation, including sharing any video from our security camera system," CTA President Dorval R. Carter Jr. said in a statement provided to Fox News.
Police said Area Three detectives are investigating the incident.
This is a developing story. Please check back for updates.