On ‘Criminal Minds’ the BAU profilers call it a “psychotic break” when a person goes nuts like this.
Essentially, something triggers and reality is lost to nearly complete delusion.
The thing is, somebody close to this punk had to have seen something was way off.
Sometimes when a troubled person makes up their mind, that can exhibit as relief or happiness. A personality change perhaps, but that could present as a positive change to those around him.
It's hard to know what someone else is "really" thinking.
This wasn't a sudden or spontaneous act. This was planned.
The thing is, somebody close to this punk had to have seen something was way off.
Too many friends and relatives are in denial about possible mental illness afflicting those closest to them.