What started as an argument quickly turned violent in a shooting at the Commerce City Santiago’s restaurant Thursday afternoon.

Police responded to the restaurant, located on East 72nd Avenue and U.S. 85, following a reported shooting at 4:07 p.m. Thursday, according to a press release from the Commerce City Police Department.

Officers arrived and found a 15-year-old boy — an employee of Santiago’s — suffering from a gunshot wound. Though the incident was originally reported as an “active shooter,” the suspect had fled by the time police arrived, spokesperson Joanna Small said in the release.

Investigators determined that the customer-turned-suspect was an adult male. The two began arguing. The fight escalated into both parties firing at one another, according to the press release. Police are still unsure if the customer was injured.

The suspect left the restaurant in the car he arrived in. The driver of that vehicle eventually pulled over and dialed 911. The suspect left the car and fled on foot. The female driver and two children in the vehicle were uninjured.

“While detectives know the identity of the customer, at this time he has not been located,” Small said. “We are reviewing surveillance footage of the incident to determine the appropriate charges for either or both parties.

The victim was transported to a local hospital with critical injuries.

Any witnesses are asked to call Commerce City Detective Sgt. Aragon at 303-727-3901.