the anti-virus measures definitely didn't "set him off", but the state of affairs might have provided him the opportunity to act out his fantasies he clearly had beforehands (which is why he had police-disguise at the ready)
Any prior mental health issues?
It should be a policy not to tell weapons to these people, and/or if they had ones (guns) before a mental illness, to have them taken away by someone,
once they get such. Crazy person + gun = bad combo.
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249
Bumb in 2021: http://gamrconnect.vgchartz.com/post.php?id=9047071