In Casas Adobes, Arizona, on 8 January 2011, a Glock 19 happened.
In Grand Rapids, Michigan, on 7 July 2011, a Glock 19 happened.
In Carson City, Nevada, on 6 September 2011, a Norinco Mak 90 happened.
In Seal Beach, California, on 12 October 2011, a Springfield 9 mm semi-automatic pistol, a .45-calibre Heckler & Koch semi-automatic pistol, and a .44 Magnum Smith & Wesson Model 29 revolver happened.
In Chardon, Ohio, on 27 February 2012, a Ruger MK III happened.
In Oakland, California, on 2 April 2012, a .45-calibre handgun happened.
In Seattle, Washington, on 30 May 2012, a Para-Ordnance .45-calibre handgun happened.
In Aurora, Colorado, on 20 July 2012, a Smith & Wesson M&P15 rifle, a Remington 870 Express Tactical shotgun, and a Glock 22 happened.
In Oak Creek, Wisconsin, on 5 August 2012, a Springfield XD(M) 9 mm semi-automatic pistol happened.
In College Station, Texas, on 13 August 2012, a vz. 58 Tactical Sporter assault rifle, a Mosin–Nagant M91/30 bolt-action rifle, a .40-calibre SIG Sauer P226 semi-automatic pistol, and a PSL designated marksman rifle happened.
In Minneapolis, Minnesota, on 27 September 2012, a Glock 19 happened.
In Brookfield, Wisconsin, on 21 October 2012, a Glock .40-calibre handgun happened.
In Newtown, Connecticut, on 14 December 2012, a Bushmaster XM15-E2S and a Glock 20SF happened.
In West Webster, New York, on 24 December 2012, a Bushmaster .223-calibre semi-automatic rifle, a Smith & Wesson .38-calibre revolver, and a Mossberg 12-gauge shotgun happened.
In Hialeah, Florida, on 26 July 2013, a Glock 17 happened.
In Saylorsburg, Pennsylvania, on 5 August 2013, a .223 Ruger Mini-14 rifle and a .44 Magnum revolver happened.
In Washington, D.C., on 16 September 2013, a Remington 870 Express Tactical 12-gauge shotgun and a Beretta 92FS 9 mm semi-automatic pistol happened.
In Terminal 3 of Los Angeles International Airport, on 1 November 2013, a .223-calibre Smith & Wesson M&P15 happened.
At Fort Hood, Texas, on 2 April 2014, a .45-calibre Smith & Wesson M&P pistol happened.
In Spring, Texas, on 9 July 2014, a Springfield XD 9 mm pistol happened.
In Marysville, Washington, on 24 October 2014, a Beretta Px4 Storm .40-calibre handgun happened.
In Tyrone, Missouri, on 26 February 2015, a .45-calibre handgun happened.
In Charleston, South Carolina, on 17 June 2015, a Glock 41 happened.
In Chattanooga, Tennessee, on 16 July 2015, an AK-47-style semi-automatic rifle, a 12-gauge shotgun, and a 9 mm handgun happened.
In Lafayette, Louisiana, on 23 July 2015, a Hi-Point .40-calibre handgun happened.
In Houston, Texas, on 8 August 2015, a 9 mm handgun happened.
In Moneta, Virginia, on 26 August 2015, a Glock 19 happened.
In Roseburg, Oregon, on 1 October 2015, a Glock 19, a Taurus 24/7, a Smith & Wesson .40-calibre pistol, and a .556-calibre rifle happened.
Note: weapons used in the shootings listed in the Wikipedia category pages for ‘mass shootings in the United States’ for the last five years. Obviously, these are only the most notorious of many, many more such incidents, as a visit to Mass Shooting Tracker will tell you.