Investigators called it an isolated incident, but there was real fear of a random, active shooter among those who were inside the crowded store.
The shooting happened around 2:56 p.m. at a Walmart store, located at t, 2500 W. 95th St. in Evergreen Park, Illinois.
Police said there was some type of argument outside the store between two male individuals.
Shots were fired outside, and then the offender pursued the other person inside while firing multiple shots in the Walmart.
The male victim, who is 23, was shot multiple times in the leg and was taken to a hospital, police said.
A 70-year-old woman, who was a bystander, also sustained a wound to her foot, possibly by a ricocheting bullet or fragment.
ABC7 spoke with Makia Barnes, a woman who is a family member of a Walmart worker, who told her about the chaos.
It was just seemed like a regular day, and then all of sudden, you just hear shooting," Barnes said. "That is ridiculous... she was just trying to find cover and safety before anything else. That was her main priority."
Police said the offender fled the store on foot. He was arrested about 15 minutes later in the neighborhood behind the Walmart, in the 9300 block of Country Club Drive. A resident called police, who then flew a drone overhead.
Video from Chopper 7 showed K-9 units in the area, also searching the location.
The suspect had arrived to the store in a Gray Hyundai, which fled the scene without him during the shooting, police said. The vehicle was later located by Chicago police in the 800 block of West Marquette in Chicago's Englewood neighborhood and taken to the Evergreen Park Police Station with the vehicle occupants.
A motive for the shooting remains unclear. Police said the male victim was taken to Christ Hospital in Oak Lawn, where he underwent surgery.
Detectives at the Evergreen Park Walmart store, which was closed Wednesday evening, began what will likely be an extensive investigation.
Walmart did not provide a comment on the situation as local police continue to investigate.