The found alcohol, sertraline, and clonazepam in his apartment.
Personally I think it is absolutely ridiculous to blame drugs for a violent crime, as people commit crimes, not drugs, but let's evaluate it from a drug standpoint...
Clonazepam is an anxiolytic. It is a drug you give to people to calm them down. They had nothing to do with this murder.
Sertraline is an anti-depressant. It's effective. If you have evil intentions, it can ease your depression and make you more ambitious to do things like violent crime if that is your agenda, but it does not cause violent thoughts. Pre-emptive mass murder is not something caused by an anti-depressant. Prisoners have their medications closely monitored, and there is no evidence of violent prisoners becoming more violent when on sertraline or the other SSRIs.
More crimes have been committed under the influence of alcohol than all other drugs combined. In fact, up to 1/3 of violent crimes involve alcohol. I'm not accusing alcohol as the cause, but if one were to pin drugs, this is the glaring front-runner.
But wait, I thought it was MK-ULTRA CIA BRAINWASHING SCOPOLAMINE ILLUMINATI? I guess now people are going back to Scientology-esque "all psychotropics are poison" arguments.