Simple. The gun used in the Connecticut school shootings would still have been legal under the assault weapons ban that liberals want to bring back. Via Reason:
"In fact, as I noted yesterday, the rifle Lanza used is not covered by Connecticut's "assault weapon" law or by the federal ban, which used similar criteria. Both laws ban the Colt AR-15 by name, but rifles not on the list of forbidden models are banned only if they have detachable magazines plus at least two of these five features: 1) a folding or telescoping stock, 2) a pistol grip, 3) a bayonet mount, 4) a grenade launcher, and 5) a flash suppressor or threaded barrel designed to accommodate a flash suppressor. The gun used by Lanza was legal in Connecticut, so it did not meet these criteria, which means it also would have been legal under the federal ban that Sen. Dianne Feinstein (D-Calif.) promises to reintroduce next month (a bill President Obama supports)."
Knee-jerk reactionaries on the left are proposing a gun ban that would have not prevented the very tragedy they have hijacked to push the gun ban.
But what more would you expect from emotional, irrational Democrats?