Shouldn’t all those Bible quotations have been a sign of a healthy and clean mind?
Well not necessarily.
Having worked with the homeless (not saying this guy was homeless) many of them use, among other things, religion as something to help them deal with drug abuse/mental illness.
A number of them were schizophrenic.
Some of them wear headphones to keep the devil from talking to them.
Obviously this guy had mental health issues. And someone sold him that gun illegally or he stole it from someone who didn’t properly secure it.