I've been researching prolific serial/spree/mass killers and sexual predators for about a decade, and in virtually every case since the 1980s, meth is the common denominator, involved either directly or indirectly. Meth creates psychopathic personalities, imo.. As in this case, domestic terrorist MJ, lacked fear, possessed a total deficit of empathy, and a complete disregard for others while carrying out his deviant acts. We will likely find that he had been tweeking on meth for days prior to the brazen kamakaze like attack, imo.
Japanese Kamikaze pilots were given high doses of methamphetamine before carrying out their suicide missions during WWII.
HISTORY OF METHAMPHETAMINE
http://www.drugfreeworld.org/drugfacts/crystalmeth/history-of-methamphetamine.html
Vanderbilt University researchers found that psychopaths are wired differently. They crave rewards, no matter the cost.
http://www.zdnet.com/article/blame-the-brain-psychopaths-are-wired-differently/