Police said the victim, 20, was beaten on the 69th Street Red Line platform and found with cuts to his head at around 7:45 p.m. That's when he was rushed to the hospital.
A 15-year-old boy was later charged with attempted murder and aggravated battery, police said.
It's still unclear what was happening in the moments leading up to this attack. Trains did bypass the 69th Street station for a couple hours as the investigation unfolded.
Police said two people of interest were taken into custody for questioning by detectives.
The video in the player above is from a previous report.
INTERACTIVE SAFETY TRACKER Track crime and safety in your neighborhood