TULSA, Okla. – Tulsa police are investigating an incident that left three shot and one person dead at a Walgreens on 71st and Lewis Wednesday afternoon.

An armed customer got into an argument with an employee in the photo department, officers told KJRH.

It is unclear at this time who shot first, but the Walgreens employee, who has a concealed-carry license, hit the suspect and killed him.

While the suspect was falling to the floor, his gun went off and a bullet grazed someone else in the store, officers say.

KJRH reports that an employee also was hit by a bullet and has non-life threatening injuries.