Responsible gun owners can and do prevent mass shootings from occurring and escalating.
A 1997 high school shooting in Pearl, Miss., was halted by the school's vice principal after he retrieved the Colt .45 he kept in his truck.
A 1998 middle school shooting ended when a man living next door heard gunfire and apprehended the shooter with his shotgun.
A 2002 terrorist attack at an Israeli school was quickly stopped by an armed teacher and a school guard.
A 2002 law school shooting in Grundy, Va., came to an abrupt conclusion when students carrying firearms confronted the shooter.
A 2007 mall shooting in Ogden, Utah, ended when an armed off-duty police officer intervened.
A 2009 workplace shooting in Houston, Texas, was halted by two coworkers who carried concealed handguns.
A 2012 church shooting in Aurora, Colo., was stopped by a member of the congregation carrying a gun.
At the recent mall shooting in Portland, Ore., the gunman took his own life minutes after being confronted by a shopper carrying a concealed weapon.