Here is a list of the 25 deadliest single day mass shootings in U.S. history from 1949 to the present. If the shooter was killed or committed suicide during the incident that death is not included in the total.
32 killed - April 16, 2007 - Virginia Tech in Blacksburg, Virginia. A gunman, 23-year-old student Seung-Hui Cho, goes on a shooting spree killing 32 people in two locations and wounds an undetermined number of others on campus. The shooter, Seung-Hui Cho then committed suicide.
27 killed - December 14, 2012 - Sandy Hook Elementary School - Newtown, Connecticut. Adam Lanza, 20, guns down 20 children, ages 6 and 7, and six adults, school staff and faculty, before turning the gun on himself. Investigating police later find Nancy Lanza, Adam's mother, dead from a gunshot wound. The final count is 28 dead, including the shooter.
23 killed - October 16, 1991 - In Killeen, Texas, 35-year-old George Hennard crashes his pickup truck through the wall of a Lubys Cafeteria. After exiting the truck, Hennard shoots and kills 23 people. He then commits suicide.
21 killed - July 18, 1984 - In San Ysidro, California, 41-year-old James Huberty, armed with a long-barreled Uzi, a pump-action shotgun and a handgun shoots and kills 21 adults and children at a local McDonalds. A police sharpshooter kills Huberty one hour after the rampage begins.
18 killed - August 1, 1966 - In Austin, Texas, Charles Joseph Whitman, a former U.S. Marine, kills 16 and wounds at least 30 while shooting from a University of Texas tower. Police officers Ramiro Martinez and Houston McCoy shot and killed Whitman in the tower. Whitman had also killed his mother and wife earlier in the day.
14 killed - August 20, 1986 - Edmond, Oklahoma part-time mail carrier, Patrick Henry Sherrill, armed with three handguns kills 14 postal workers in ten minutes and then takes his own life with a bullet to the head.
13 killed - April 3, 2009 - In Binghamton, New York, Jiverly Wong kills 13 people and injures four during a shooting at an immigrant community center. He then kills himself.
13 killed - April 20, 1999 - Columbine High School - Littleton, Colorado. 18-year-old Eric Harris and 17-year-old Dylan Klebold kill 12 fellow students and one teacher before committing suicide in the school library.
13 killed - September 25, 1982 - In Wilkes-Barre, Pennsylvania, 40-year-old George Banks, a prison guard, kills 13 people including five of his own children. In September 2011, the Pennsylvania Supreme Court overturns his death sentence stating that Banks is mentally incompetent.
13 killed - September 5, 1949 - In Camden, New Jersey, 28-year-old Howard Unruh, a veteran of World War II, shoots and kills 13 people as he walks down Camden's 32nd Street. His weapon of choice is a German-crafted Luger pistol. He is found insane and is committed to a state mental institution. He dies at the age of 88.
12 killed - September 16, 2013 - Shots are fired inside the Washington Navy Yard killing 12. The shooter, identified as Aaron Alexis, 34, is also killed.
12 killed - July 20, 2012 - Twelve people are killed and 58 are wounded in a shooting at an Aurora, Colorado, movie theater screening of the new Batman film. James E. Holmes, 24, is taken into custody outside of the movie theater. The gunman is dressed head-to-toe in protective tactical gear, set off two devices of some kind before spraying the theater with bullets from an AR-15 rifle, a 12-gauge shotgun and at least one of two .40-caliber handguns police recovered at the scene.
12 killed - July 29, 1999 - In Atlanta, 44-year-old Mark Barton kills his wife and two children at his home. He then opens fire in two different brokerage houses killing nine people and wounding 12. He later kills himself.
10 killed - March 10, 2009 - In Alabama, Michael McLendon of Kinston, kills 10 and himself. The dead include his mother, grandparents, aunt and uncle.
9 killed - March 21, 2005 - Red Lake High School, Red Lake, Minnesota. 16-year-old Jeff Weise kills his grandfather and another adult, five students, a teacher and a security officer. He then kills himself.
9 killed - June 18, 1990 - In Jacksonville, Florida, 42-year-old James Pough, angry about his car being repossessed, opens fire at at a General Motors Acceptance Corp. office, killing nine people. Pough takes his own life.
8 killed - October 12, 2011 - Eight people are killed during a shooting at the Salon Meritage in Seal Beach, California. The suspect, Scott Evans Dekraai, 41, of Huntington Beach, is arrested without incident as he is trying to leave the scene. The eight dead include Dekraai's ex-wife, Michelle Fournier, 48. He was armed with three guns -- a 9 mm Springfield, a Smith & Wesson .44 Magnum, and a Heckler & Koch .45 -- and was wearing body armor during the shooting rampage.
8 killed - August 3, 2010 - Manchester, Connecticut - Omar Thornton kills eight co-workers at Hartford Distributors before turning the gun on himself. Thornton had been asked to resign for stealing and selling alcoholic beverages.
8 killed - January 19, 2010 - Christopher Speight, 39, kills eight people at a house in Appomattox, Virginia. He surrenders to police at the scene the next morning, and is charged with one count of murder with additional charges pending.
8 killed - March 29, 2009 - In Carthage, North Carolina, 45-year-old Robert Stewart kills a nurse and seven elderly patients at a nursing home. In May, the Moore County district attorney announces she will seek the death penalty. On September 3, 2011, a jury finds Stewart guilty of second-degree murder. Stewart is sentenced to 141 to 179 years in prison.
8 killed - December 5, 2007 - In Omaha, Nebraska, 19-year-old Robert Hawkins goes to an area mall and kills eight shoppers before killing himself.
8 killed - July 1, 1993 - In San Francisco, 55-year-old Gian Luigi Ferri kills eight people in a law office and then kills himself.
8 killed - September 14, 1989 - In Louisville, Kentucky, 47-year-old Joseph Wesbecker armed with a AK-47 semiautomatic assault rifle, two MAC-11 semiautomatic pistols, a .38 caliber handgun, a 9-millimeter semiautomatic pistol and a bayonet kills eight co-workers at Standard Gravure Corporation and then kills himself. He had been placed on disability leave from his job due to mental problems.
8 killed - August 20, 1982 - In Miami, 51-year-old history teacher Carl Robert Brown, angry about a repair bill and armed with a shotgun, kills eight people at a machine shop. He flees by bicycle, but is shot in the back by a witness who pursued him. He was on leave from school for psychological treatment.