An Air Force vet shot and killed one of two armed robbery suspects who pistol-whipped him as he worked behind the register of a California convenience store, according to a report.

Mark Kasprowicz, 56, said his “instinct just kicked in” when he was ambushed behind the register Sunday night at Kam’s Market in Bay Point, news station KTVU reported.

“Fear and adrenaline kicked in together. I’m lucky to be alive,” Kasprowicz, a manager at the store, told the outlet.

Kasprowicz said he initially didn’t know what to believe when the two suspects entered the convenience store around 11 p.m. while he was counting cash.

One of the suspects held him at gunpoint while the other man stole money from the register, the report said.

“At first, I thought it was a joke,” Kasprowicz said.

But video shows the crook at the register then strike Kasprowicz with his gun, knocking him to the floor. The criminal was wearing a bandanna and sunglasses.

The assailant then grabs more money as he pummels the vet with his other hand and pistol-whips him again.

Kasprowicz eventually was able to grab his own gun, which he fired after the crook shot holes in the ceiling and into a sunglasses case, according to KTVU.

Kasprowicz struck his assailant, who ran outside and collapsed half a block away, the report said. The perp died of his injuries Sunday night.

Authorities are still looking for the accomplice, who was seen on surveillance video approaching the counter and running outside, according to KTVU.