HOUSTON, Texas (KTRK) — A shopper at a southeast Houston convenience store opened fire when four masked robbers stormed inside, sending three suspects to the hospital.

Houston police said at least one of the robbery suspects was armed.

HPD officers were called to a Circle K convenience store at a Valero gas station located at 8040 South Loop East at 7:55 p.m. Thursday.

According to Asst. Chief Ernest Garcia, four suspects in masks entered the store and started robbing customers at gunpoint.

That’s when an armed customer pulled out their weapon and shot at the suspects, Garcia said. Three of the robbery suspects were shot.

One bystander was also hurt, though it was unclear if he was shot by one of the suspects or the customer, HPD said.

All four suspects ran out of the store and to a car outside, where a fifth suspect was waiting, investigators said.

Meanwhile, the bystander was taken to the hospital via ambulance in stable condition.

The suspects left the scene and drove to a nearby hospital. One suspect who was shot is in critical condition, and the other two are stable, Garcia said.

In total, four suspects are in custody and one is still wanted, according to HPD.

Garcia said investigators believe the suspects are young males — possibly juveniles — though their exact ages are unknown.