"An aggie, one of the" joke

An aggie, one of the elderly types, proceeded to try out
for a part in a local College Station play. Sympathizing
with his zeal for the part, the cast director agreed to
include him in it, but under two conditions, he'd better do
a heck of good job, and he would only get one line in the
entire play: "Hark! the cannon just fired!"
So the elderly aggie goes home, brags to all his friends about it,
and continually yells:
"Hark! the cannon just fired!"
"Hark! the cannon just fired!"
Finally on the night of the performace, during the highlight of
the play, the booming sound of a menacing cannon shakes the
entire theatre, the audience, in complete awe and silence...
At the top of his lungs the aggie shouts:
"What the hell was that?!"