Bombing at the Boston Marathon

This is probably not true, but the only thing worse than whatever motivates someone to commit such a bloody crime is whatever motivates people (left, right, center, askew) to immediately speculate on who "probably did it".

And, yes, on the assumption that it was not an accidental detonation, then it is by definition simple mass killings or, if motivated to scare people and drive particular social and political actions, terrorism.  Again, by definition.

But that doesn't actually tell you anything about who did it, who needs to be caught and punished, and certainly doesn't actually tell you anything about the rational public policy (including national security) response should be to prevent it from happening again (on the assumption that one can prevent public bombings if you have enough people determined to do them).

Want something to do that's more productive than playing politics, or playing a guessing game, or drawing up new national security and police measures that have little or nothing to do with what happened?  Try donating to some of the organizations helping the victims here.  Or, heck, say a prayer for the dead and injured and their families and friends — whether or not it will do any  good, it's a lot less likely to do harm than picking which group to smear with this crime before there's any actual, y'know, evidence about it.