Oct. 2 (UPI) -- With at least 50 dead, the shooting at a Las Vegas concert on Sunday qualifies as the worst mass shooting in U.S. history.
The FBI defines a mass killing as an attack in which three or more people are killed in a public space.
The worst in United States history have involved guns. Here are some of the deadliest in recent years.
Pulse nightclub, Orlando, Fla.
Forty-nine people were killed and 58 injured when a lone gunman opened fire in a crowded gay nightclub in Orlando, Fla., on June 12, 2016. The lone gunman, Omar Mateen, 29, was killed by police at the club. At the time of the shooting, Mateen pledged allegiance to the Islamic State.
Virginia Tech University, Blacksburg, Va.
On April 16, 2007, student Seung Hui Cho, 23, shot and killed 32 people before killing himself at Virginia Tech University in Blacksburg, Va. Seung, who was carrying two handguns, had a history of psychological problems.
Sandy Hook Elementary School, Newtown, Conn.
Adam Lanza, 20, shot at killed 20 students and six adults at Sandy Hook Elementary School in Newtown, Conn., before killing himself on Dec. 14, 2012.
Luby's restaurant, Kileen, Texas
This Oct. 16, 1991, shooting remained for many years as the deadliest shooting in U.S. history. George Hennard, 35, shot 23 people dead before killing himself. Several witnesses said Hennard passed over multiple men in the restaurant to shoot women.
McDonald's restaurant, San Diego, Calif.
Twenty-one people -- including several children -- were shot dead by gunman James Huberty on July 18, 2984, in a suburb of San Diego. Hubert remained inside the restaurant for more than an hour before a police sniper shot him dead. Hubert had just lost his job and suffered from psychological illness.
University of Texas tower, Austin, Texas
Marine sharpshooter Charles Joseph Whitman perched himself atop the Main Building tower at the university and opened fire, killing 16 people on Aug. 1, 1966. A police officer ultimately climbed the tower and shot Whitman. An autopsy found a small tumor on his brain.
U.S. Post Office, Edmunds, Okla.
Part-time mail carrier Patrick Sherill shot 14 postal workers on Aug. 20, 1986, before he killed himself. The attack is largely credited with helping create the term, "going postal."
Inland Regional Center, San Bernardino, Calif.
Fourteen people died and 22 were injured on Dec. 2, 2015, when Syed Farook and Tashfeen Malik opened fire at a holiday party at the San Bernardino County, Calif., Department of Health, where Farook worked. He earlier pledged allegiance to the Islamic State.
Military base, Fort Hood, Texas
U.S. Army Maj. Nidal Hassan Hasan shot 13 people to death on Nov. 5, 2009, at the Fort Hood military base in Texas. He was convicted and sentenced to death.
Washington Naval Yard, Washington, D.C.
Aaron Alexis, 34, killed 12 people and injured three others in a rampage on Sept. 16, 2013 at the Naval Sea Systems Command in Washington, D.C. Police shot him to death.
Movie theater shooting, Aurora, Colo.
Emanuel AME Church shooting, Charleston, S.C.
Dylann Roof, 21, shot and killed nine parishioners of a Charleston, S.C., church on June 17, 2015, in what police and prosecutors say was a racially motivated crime.