The St. Louis Metropolitan Police department is investigating a deadly officer-involved shooting in south St. Louis.

According to police, the incident started around 11:40 p.m. on Tuesday when a man walked into the Shell gas station on Arsenal Street and demanded money from the cashier.

The suspect has been identified as Chazz Brown, 33, of Columbia.

Investigators say an off-duty, plainclothes officer was inside at the time and he identified himself. They say there was then an exchange of gunfire. The suspect was shot and killed.

Police say there were two clerks and a customer inside at the time. No one else was hurt.

The officer is a 7-year veteran of the force and had just gotten off his shift.

The gas station is also used as a police substation. Officers use the substation to conduct police business such as use the phone and write reports.

Per department policy, the officer involved in the shooting will be placed on administrative leave. An investigation is ongoing.