The private who was manning the guard post at the gate came running along behind, probably worried that somebody had been hurt in the crash. The general hops out of the cab and unloads on the poor kid with both barrels of choice insults about the private's parentage, IQ, social standing and hygiene, finishing it off with "and why the hell didn't you shoot me?!"
According to legend, that was what the private was punished for -- dereliction of duty, failing to shoot the threat to base security.
(Obviously, this story is most likely complete BS.)