The real question is now: Who is Trayvon Martin and why did he jump George Zimmerman?
Maybe he was paranoid. He was kicked out of school for bringing narcotics in.
He was 17, impulsive, trained in violence (football), and obviously not the Golden Boy his parents lied about.
Most cannabis users, are not inclined to violence. Cf. ethanol. But for all psychotropics, its the individual, not the material.