The gunman has been taken into custody after shooting at Stoneman Douglas High School in Florida.
The bloodshed in Florida was the latest outbreak of gun violence that has become a regular occurrence at U.S. schools and colleges. Below are some of the worst U.S. school shootings in the last 20 years.
• BENTON, Kentucky, Jan. 23, 2018 - Gabe Parker, 15, kills two fellow students,both also 15, at Marshall County High School in western Kentucky with a pistol and wounds 14 others. Four other high schoolers suffered non-gunshot wounds in the ensuing panic.
• AZTEC, New Mexico, Dec. 7, 2017 - William Atchison, a 21-year-old man, disguised as a student enters the local high school, kills two students and then shoots himself to death.
• SAN BERNARDINO, California, April 10, 2017 - Cedric Anderson dies of a self-inflicted gunshot wound after killing his estranged wife at North Park Elementary School where she worked. An 8-year-old student is also shot to death.
• ROSEBURG, Oregon, Oct. 1, 2015 - Chris Harper-Mercer, 26, opens fire on the campus of Umpqua Community College, killing nine people before he is shot dead by police.
• MARYSVILLE, Washington, Oct. 24, 2014 - Freshman student Jaylen Fryberg, 15, at Marysville-Pilchuck High School fatally wounds four students in the cafeteria before killing himself.
• SANTA MONICA, California, June 7, 2013 - A onetime digital media student, John Zawahri, 23, fatally shoots his father and brother, sets their house on fire, and then kills three people at Santa Monica College. The gunman kills himself.
Newtown Police Officer Maryhelen McCarthy carries flowers near a memorial for shooting victims of Sandy Hook Elementary School. Photo / AP
• NEWTOWN, Connecticut, Dec. 14, 2012 - Adam Lanza, 20, fatally shoots his mother, then kills 20 children and six adults before killing himself at Sandy Hook Elementary School. It was the deadliest mass shooting at either a high school or grade school in US history and prompted renewed debate about gun control in the United States.
• OAKLAND, California, April 2, 2012 - One L Goh, a former nursing student, kills seven people and wounds three at Oikos University, a Korean Christian college.
• CHARDON, Ohio, Feb. 27, 2012 - Seventeen-year-old student Thomas 'T.J' Lane at Chardon High School kills three students and wounds three in school cafeteria. He received three life sentences on March 19, 2013. In 2014, Lane, along with two other inmates, escaped from Allen Correctional Institution in Lima, Ohio, but he was recaptured the following day.
• HUNTSVILLE, Alabama, Feb. 12, 2010 - Amy Bishop, a biology professor at the University of Alabama at Huntsville opens fire during a staff meeting, killing three faculty members and wounding three.
• DEKALB, Illinois, Feb. 14, 2008 - Steve Kazmierczak, a former graduate student, kills five students and wounds 16 at Northern Illinois University before taking his own life.
• BATON ROUGE, Louisiana, Feb. 8, 2008 - Nursing student Latina Williams at Louisiana Technical College kills two classmates and herself in a classroom.
A man prays at the site of a makeshift memorial left on the Virginia Tech campus. Photo / AP
• BLACKSBURG, Virginia, April 16, 2007 - Gunman Seung-Hui Cho slaughters 32 people and kills himself at Virginia Polytechnic Institute and State University, popularly known as Virginia Tech. At the time it was the deadliest shooting carried out by a single gunman in US history.
• NICKEL MINES, Pennsylvania, Oct. 2, 2006 - Gunman Charles Carl Roberts IV took hostages and shot eight out of 10 girls, killing five in a one-room Amish schoolhouse, before killing himself.
• SHEPHERDSTOWN, West Virginia, Sept. 2, 2006 - 49-year-old Douglas Pennington shoots himself and his two sons Logan, 26, and Benjamin, 24, to death during a visit to the campus of Shepherd University.
• RED LAKE INDIAN RESERVATION, Minnesota, March 21, 2005 - A 16-year-old high school student Jeffrey Weise, kills seven people including his grandfather, a tribal police officer, and wounds several others in a shooting rampage after killing two people off-campus. He then kills himself.
• COLD SPRING, Minnesota, Sept. 24, 2003 - Fifteen-year-old student John Jason McLaughlin, fatally shoots a freshman and a senior at Rocori High School.
• TUCSON, Arizona, Oct. 29, 2002 - Failing student Robert S Flores Jr, 41, shoots and kills three professors and then himself at the University of Arizona School of Nursing.
• GRUNDY, Virginia, Jan. 16, 2002 - Nigerian immigrant Peter Odighizuwa, a recently dismissed graduate student aged 41, kills a dean, a professor and a student at the Appalachian School of Law and wounds three others.
• SANTEE, California, March 5, 2001 - Charles Andrew Williams, a student at Santana High School kills two students, wounds 13. He is currently serving life in prison.
A family visits the memorial crosses dedicated to the the 13 people killed in the 1999 Columbine High School shooting attack. Photo / AP
• LITTLETON, Colorado, April 20, 1999 - Two teenagers Eric Harris and Dylan Klebold rampage through Columbine High School, fatally shooting 12 students and a teacher and wounding more than 20 others before killing themselves. The personal journals of the duo document that they wanted their actions to rival that of the Oklahoma City bombing.
• JONESBORO, Arkansas, March 24, 1998 - Two boys Mitchell Johnson, 13, and Andrew Golden, 11, fire on their middle school from woods, killing four girls and a teacher and wounding 11 others.
