Police say a 24-year-old man was shot in the abdomen and transported to Lutheran General Hospital at around 4:35 p.m.
The initial investigation indicates the shooting was a result of a dispute involving a custody exchange of a child, according to a Rolling Meadows Police release.
WATCH: More video from scene
It began as a physical altercation in the parking lot and escalated to shots being fired between individuals involved in the dispute, officials said.
Some shoppers were forced to wait for hours while officer conducted their investigation because their cars were blocked off with police tape.
"I was wondering what was going on," said Michelle Mann. "We were just here two hours ago and coming back to return some and this was all here."
Detectives say they are interviewing the individuals involved.
"It is scary, I am just happy that we got here after it happened and not during because we have children," said Daisy Espino.
ABC 7 Chicago has reached out to Walmart for comment, but a spokesperson referred us to police since the shooting happened outside of the store.