CHICAGO — Two men are injured after a shooting in a Walgreen’s store in the city’s Old Town neighborhood, police said.

According to police, a 26-year-old man was working at a 24-hour Walgreens in the 1600 block of North Wells Street around 11:55 p.m. when a man in his late twenties entered the store, had an altercation with the employee and produced a gun.

Police said gunfire was exchanged and the employee sustained a graze wound to the chest. He refused medical attention on the scene.

The offender sustained gunshot wounds to the chest, head, abdomen and self-transported to Northwestern Memorial Hospital in critical condition.

Police said the two appeared to have known each other and investigators have not disclosed additional details about what prompted the fight.

It is still unknown whether the employee is a CCL holder and the company does ban guns inside store locations.

There is currently no one in custody and police are investigating the incident.

“The safety of our patients, customers and team members is our top priority,” a statement from Walgreens read. “We take this matter seriously and are cooperating with the Chicago Police Department.”