In response to the nearly unbelievable Virginia Tech tragedy, Brown University officials have decided to implement a warning system--a very loud one. In the event that somebody tries anything of the V-tech sort, various sirens would alert the campus (and in effect, all of Providence). 

"The sirens, which would be installed in three locations across campus, would be loud enough to be heard around the area, and have voice capability so that information about the nature of the emergency could be broadcast."

So let's say a situation occured (knock on wood): how exactly would the attacker be stopped by the piercing alarms, resulting campus-wide chaos and potential aggravation of said situation?

An all-encompassing campus safety plan is certainly important, especially in the wake of the V-Tech tragedy, but is this really the way to go about it?