Sorry to say - that if you search you can find police stations and courts being shot up. It's not a telling argument against the suicidal run from someone who wants to kill and then die.
Search on it. Tyler court house for instance. There are others.
Look at this guy - http://abcnews.go.com/US/christopher...ry?id=18427632
The reason for the gun, primarily, is to reduce the impact of the incident as the shooter can be engaged more quickly.