"I don't go out at night, but I do walk around the neighborhood," said Giuseppe Marento, who lives in the area.
The 42-year-old bicyclist was riding in the 1200-block of West Montrose Drive at about 10:52 p.m. when police said he observed a male suspect trying to break into a vehicle.
The bicyclist attempted to confront the suspect, who took out a weapon and shot the victim before fleeing on foot, police said.
Investigators say when the Good Samaritan confronted the alleged thief, the robber pulled out a gun and opened fire on the bicyclist, not only striking him in the elbow, but also left a pickup truck riddled with bullets.
A woman, who did not want to be identified, said the pickup is her work vehicle.
"I was getting ready for bed, watching a little bit of TV and heard, very loud, several gunshots and startled me," she said. " It sounded like it was very close...I came out to take my dog for a walk and came around the corner on a regular route and I park my work truck on Montrose and as I was walking by I noticed that there were bullet holes in my work truck."
Police said black Jeep Grand Cherokee, with another vehicle following behind it were spotted leaving the scene, traveling eastbound.
No one is in custody. Area Three detectives are investigating.