The 34-year-old man was inside his home in the 6100-block of South Vernon Avenue in the city's West Woodlawn neighborhood when a bullet came through a window around 10:30 p.m., police said.
The victim was transported to University of Chicago Medical Center, where he is listed in serious condition.
The man's roommate said the bullet came out of nowhere and believes the victim, "my brother," was an innocent bystander.
Investigators have not said if he was the intended target. CPD officials said he is "not known to police."
The roommate said the victim is not angry about what happened, and that sadly, innocent people get hit all too often by gunfire.
No one is in custody.