wileydog3 . . . yes, it's understood by most reasonable people and above all by aeronautical engineers that a tiny hole in the fuselage made by a tiny bullet as such would not cause depressurization.
The larger issue is whether the cockpit side window [with 2 tons of pressure per square inch at high altitude, for example] would have maintained its integrity or would have shattered, . . . in which case there would have been a hole much larger than both outflow valves combined [as on a 747].
From the A319 cockpit photos it is apparent that this bullet hole was only about 12 inches from hitting the side window which is not as thick and sturdy as the forward facing windscreens.
And if the bullet in fact was fired from the copilot's gun, then its trajectory was too close across the captain's knees for comfort. So this would not be just a simple forget-about-it accidental discharge of a deadly weapon, but something like "attempted, involuntary manslaughter" due to gross negligence.
This is not a scenario which USAir nor its pilots' union can easily keep low key. In fact this incident will likely trigger a bottoms up training review of the FFDO program, if not its termination altogether. Most pilots and most passengers are not happy with guns in the cockpit; and the media buzz about this incident will drive this message home to congress and more importantly to the mental midgets at the TSA who authorized this program.