A robbery suspect at a Shell gas station on the city's Northwest Side wound up being shot in the buttock Sunday night by a customer.

The suspect, 35-year-old Dustin Durst, entered the station store in the 10100 block of Culebra Road with what appeared to be a handgun, San Antonio police Det. Roberto Bernal said. Really, it was a hammer no more than 6 inches long, draped in a black cloth or sock.

“He carried it as if it was a gun and pointed it at the clerk and the customer,” Bernal said. “He wanted them to believe that what he had was a gun.”

Durst apparently grabbed a box of K2, which mimics the effects of marijuana, put it in a black satchel and walked out. But the customer followed him outside and confronted him in front of the building, Bernal said.

“The robber still wanted the guy to believe he had a gun but ended up dropping it,” he said. “And as he was going to reach for it, the (customer) shot him in his left upper buttock.”

Durst was taken to University Hospital but did not have a life-threatening wound.

The customer isn’t facing any charges for the shooting, which occurred around 9:30 p.m., Bernal added.

“According to Title 2, Chapter 9 of the Penal Code, you can use deadly force to protect property and prevent the other’s imminent commission of robbery,” he said. “So he’s covered under that."