The problem I see is there was only one armed student on campus mutable armed students/staff would have upped the odds that there would have been a defender with in seconds instead of hundreds of yards away.
The decision to stay and defend or go on the attack depends on many things I wouldn't condemn him for staying and defending.
A lone person going on the offensive is very vulnerable so much depends on the information one has.
The farther the distance away the less info one has.
Good bad or other wise it is a personal choice.