A motive is emerging (Sandy Hook shooting)

[HooptieWagon]

78. Both killed more than Sandy Hook, however.

And the biggest school massacre in history was the result of dynamite. Let's not forget the ATL Olympic bombing, numerous church arsons and bombings, abortion clinic bombings and arsons, and the FACT that Columbine was intended to be a bombing. Several bombs made from propane tanks failed to go off due to faulty timing mechanisms. The killers planned to kill 600. Unlikely, but even 10% of that number would have been far greater than the gunshot deaths.

Mass murderers are going to commit their crimes with whatever weapons they can easily acquire. Example: http://www.sptimes.com/News/102900/TampaBay/Community_finally_ris.shtml Yes, often it's guns of one type or another. Otherwise it's fertilizer, propane, lighter fluid, etc. The Sandy Hook killer could have simply rammed his mother's car into a crowd of schoolkids waiting to board schoolbuses, with equally devastating results.
This doesn't mean we should throw up our hands and despair and do nothing. But let's take a big picture approach in preventing these events, rather than a narrow focus.