Good deal. In Colorado anyone can have a gun in the car without a permit. So far, no mass shootings.
In Texas, in 1966, lots of people pulled long guns down from the gun racks in the back windows of their pickup trucks and returned the unfortunate (brain-tumor-addled) Charles Whitman's deadly fire.
After the Texas citizens started returning fire, Whitman killed no more pedestrians within range of his weapon (a scoped M-1 carbine iirc -- he was an ex-Marine sharpshooter) until two Austin cops and a shotgun-carrying civilian could get up the clock tower to kill him.