A Mississippi gun shop owner and his 17-year-old son were killed Saturday in a shootout in their store with two customers — also a father and son — apparently after an argument over a service charge.

The customers — a man in his 50s and his son in his 20s, WLOX-TV reported — went to the McLemore Gun Shop on Highway 43 in Pearl River County around 3:15 p.m. to pick up a gun, County Sheriff David Allison told the station.

But when the customers were told the gun hadn’t been repaired — and that they would have to pay a $25 service fee — one of the customers got upset, Allison told WLOX. The Sun Herald reported that it had been repaired but that a $25 service fee was owed.

The wife of the 40-year-old gun shop owner was at the counter and called her husband and son to deal with the dispute, WLOX said. The Sun Herald reported that the woman called her husband who soon emerged with his son.

An argument ensued, which turned physical, the station said, and gunfire followed.

Chief Deputy Shane Tucker told the Sun Herald that ”one of the customers and one of the owners produced firearms. We don’t know who shot first.”

The gun shop owner and his son were pronounced dead at the scene; the two customers were airlifted to hospitals with life-threatening injuries, Tucker told the paper.

The wife of the gun shop owner was not wounded, WLOX reported.

This story has been updated.