OAKLAND (KPIX 5) — A business owner who had been robbed at gunpoint Monday morning in Oakland chased the robbers with his own gun and exchanged gunfire with them, with a stray bullet piercing a home and hitting a resident inside, according to authorities.

The incident happened at a coin exchange business on the 3300 block of Grand Ave. just before 10 a.m., police said.

Business owne Charlie Mammoser said he wasn’t thinking when he buzzed in two men wearing masks into his coin shop. “Well, they came in, they had their guns pulled out, they walked in and they were ready to go,” said Mammoser. “And they ordered me to get down on the floor, face down.”

Mammoser said his safe was open and the crooks filled a bag with about 100 pounds of rare silver bouillon coins. They then ran out the store and up the hill.

And something inside Mammoser snapped.

“After they were gone, I realized what just happened. I grabbed my gun and went after them …. and I saw one of the guys still on the street around the corner there ,” said Mammoser. “And I told him, ‘Hey, stop!‘ And I had my gun and I point it at him. And he turned around, and shot at me, so I shot at him twice.”

Just then, the second robber drove up in a car, and the gunfire continued.

“He’s shooting at me, and I shot at him,” said Mammoser. “And hit his car. I don’t know what I hit. And I’m told that he hit the window next to me, and he hit somebody.”

The crooks dropped the bag of coins and took off. Mammoser, who was uninjured, could not carry that heavy bag so he dragged it back to the store and called police.

Oakland Police Officer Johnna Watson said it’s too early to tell if Mammoser will face charges, but has a message to any citizen who decides to take matters into their own hands.

“That everyone’s safety is important,” said Watson. “Anytime you’re going to take action, if you are a victim of a crime, to think about our community, our neighborhood, our children, residents who are around us.”

Claudia Hartley, who lives next door to the man who was shot, says he got hit in leg and will be okay. Police said he was listed in stable condition at a local hospital.

Hartley also knows Mammoser. When asked whether she would you go as far to say it was careless and irresponsible to go after the armed robbers, Hartley replied, “I wouldn’t do it myself. But I’m not going to second-guess Charlie.”

Mammoser was asked whether if he could go back in time, what would he do differently.

He responded, “Take Monday off.”