Horrific incidents like the 2012 Sandy Hook Elementary School shooting put a renewed spotlight on gun violence, but dozens of American lives have been claimed in mass shootings since 2000, many of which involved the use of semiautomatic weapons.
 
The below list offers a glimpse of some, but not nearly all, highly publicized shootings in the U.S. involving a lone gunman that claimed at least four lives.
 
Dec. 26, 2000 — Wakefield, Mass.
Michael McDermott, 42, shot and killed seven coworkers at Edgewater Technology using several weapons, including an AK-47.
 
March 12, 2005 — Brookefield, Wis.
Terry Ratzmann, 44, shot and killed seven members of the Living Church of God at a Sheraton hotel with a 9mm handgun before committing suicide.
 
March 21, 2005 — Red Lake, Minn.
Jeffrey Weise, 16, shot and killed 10 people before turning the gun on himself, including his grandfather and a police officer, using several weapons, including a 12 gauge shotgun.
 
Jan. 30, 2006 — Goleta, Calif.
Former postal worker Jennifer San Marco, 44, shot and killed seven people, including several former coworkers, and herself.
 
Oct. 2, 2006 — Lancaster County, Pa.
Charles Carl Roberts IV shot and killed five female students inside an Amish schoolhouse using several weapons before committing suicide.
 
Feb. 12, 2007 — Salt Lake City, Utah
Sulejman Talovic, 18, killed five people at Trolley Square Mall with two weapons before he was shot and killed by police.
 
April 16, 2007 — Blacksburg, Va.
College student Seung-Hui Cho shot and killed 32 people on the campus of Virgina Tech with two weapons before taking his own life.
 
Oct. 7, 2007 — Crandon, Wis.
Sheriff's deputy Tyler Peterson, 20, shot and killed six people at a post-Homecoming party in an apartment before committing suicide. He used a semiautomatic rifle.
 
Dec. 5, 2007 — Omaha, Neb.
Robert A. Hawkins killed eight people and himself using a semiautomatic rifle after entering the Westroads Mall.
 
Feb. 2, 2008 — Kirkwood, Mo.
Charles Lee Thornton, 52, entered a public city council meeting and shot and killed five people with two handguns before he was shot and killed by police.
 
Feb. 14, 2008 — Dekalb, Ill.
Steven Kazmierczak, 27, shot and killed five people on the campus of Northern Illinois University with several semiautomatic weapons before killing himself.
 
June 25, 2008 — Henderson, Ky.
Wesley Neal Higdon, 25, killed five people at Atlantis Plastics Factory with a semiautomatic weapon before taking his own life.
 
April 3, 2009 — Binghamton, N.Y.
Jiverly Antares Wong, a 41-year-old naturalized American citizen from Vietnam, shot and killed 14 people at the American Civic Association with two weapons before killing himself.
 
August 3, 2010 — Manchester, Conn.
Omar Thorton, 34, entered a warehouse owned by his former employer, Hartford Distributors, and shot and killed eight people with two semiautomatic weapons before committing suicide.
 
Sept. 6, 2011 — Carson City, Nev.
Eduardo Sencion, 32, opened fire with a semiautomatic rifle in an IHOP restaurant, killing four people and himself.
 
July 20, 2012 — Aurora, Col.
James Holmes, 25, shot and killed 12 people in a movie theater during the premier of "The Dark Knight Rises" using several weapons, including a semiautomatic rifle.
 
Aug. 5, 2012 — Oak Creek, Wis.
Wade Michael Page, 40, killed four people with a semiautomatic weapon inside a Sikh temple before turning the gun on himself.
 
Dec. 14, 2012 — Newtown, Conn.
Adam Lanza, 20, shot and killed his mother and 26 people inside Sandy Hook Elementary School before turning the gun on himself.
 
March 13, 2013 — Herkimer, N.Y.
Kurt Meyers, 64, killed four people at a carwash and barber shop with a shotgun before he was shot and killed by police.
 
Sept. 16, 2013 — Washington, D.C.
Aaron Alexis, 34, shot and killed 12 people inside the Washington Navy Yard with a 12-gauge shotgun before he was shot and killed by police.
 
June 7, 2013 — Santa Monica, Calif.
John Zawahri, 23, opened fire in a home and later on the campus of Santa Monica College, killing five people with a semiautomatic rifle. He was killed during a shootout with police.
 
July 26, 2013 — Hialeah, Fla.
Pedro Alberto Vargas, 42, shot and killed six people with a semiautomatic weapon in his apartment complex before setting fire to his own apartment. He was shot and killed by a SWAT team.
 
September 14, 2014 — Bell, Fla.
Don C. Spirit, 51, shot and killed his granddaughter and six grandchildren before turning the gun on himself. 
 
May 17, 2015 — Waco, Tx. 
 
Rival motorcycle gangs kill nine at a restaurant in Waco, Texas. There were over 170 arrests made after the incident. 
 
June 17, 2015 — Charleston, S.C.
Dylann Roof, 21, walks into am historic black church in Charleston, South Carolina and kills nine people.
 
 
Oct. 1, 2015 — Roseburg, OR.
Christopher Harper-Mercer enters Umpqua Community College in southwest Oregon, opens fire and kills nine, wounding seven others before police shoot him to death. 
 
November 27, 2015 — Colorado Springs, CO
 
Robert Lewis Dear storms in a Planned Parenthood health clinic in Colorado Springs, Colorado and kills three people and wounding nine.  
 
December 2, 2015 — San Bernardino, CA. 
 
A man and a woman walk into a holiday party both armed with assault weapons and kill 14 people and wounding 17 others. 
 
June 12, 2016 — Orlando, FL. 
 
Omar Mir Seddique Mateen, 29, killed 50 people and injured 53 at Pulse – a popular gay nightclub in Orlando, Florida. This is the worst mass shooting in US history. President Barack Obama described the horrific event as an "act of terror and hate."