I was going to make a snarky comment about how maybe we need to require background checks on purchases of pressure cookers. But since I hold to the non-aggression axiom I must decry the recent incident at the Boston Marathon. No political grievance ever justifies the use of violence against an individual's person or property.
"No one may threaten or commit violence ('aggress') against another man's person or property. Violence may be employed only against the man who commits such violence; that is, only defensively against the aggressive violence of another. In short, no violence may be employed against a nonaggressor."