Police responded to the fire and found CFD already on the scene at 11:32 p.m. in the 4700-block of West Ohio Street.
Video from the scene showed heavy smoke and flames coming from that apartment building. Firefighters could be seen on ladders, smashing the building's windows.
It's apparent that the back of the building is also heavily damaged.
A 33-year-old man suffered burns to his arms and face and transported to Loyola University Medical Center in critical condition., police said.
An 81-year-old man and 64-year-old woman, both suffered from smoke inhalation and were transported to Mt. Sinai Hospital in serious condition, police said.
The cause of the fire is under investigation.