Officers initially responded to a call of shots fired at Albany Avenue and 96th Place about 5:50 a.m., but they couldn't find anything, police Capt. Greg LeCompte said.
But less than an hour later, an officer heard shots fired from the direction of the man's home and gave chase down an alley, spotting a garage door slamming shut at his house, LeCompte said.
He said police surrounded the home and knocked on the door, but the man who answered claimed to be a guest. Officers then found the homeowner inside, and a witness identified him as the person firing shots in the alley, LeCompte said.
Illinois State Police dogs helped officers locate guns and ammunition hidden throughout the house, while dogs with the Cook County sheriff's police bomb unit also searched the home.
"We don't know why he had all these weapons," Saunders said.
Authorities still were at the house Friday night, and the man is not expected to be charged until today at the earliest, Saunders said.
He said the man, who is not being identified because he has not been charged, was taken to Christ Medical Center in Oak Lawn after complaining of chest pains Friday afternoon.