After a gunman killed more than 50 people at a Las Vegas concert Sunday, here are some of the deadliest mass shootings in the United States in the past 25 years.
A heavily-armed gunman opened fire inside a gay nightclub in the city of Orlando on June 12, 2016 and killed 49 people.
The attacker was killed in a shootout with police; he pledged allegiance to the Islamic State group, which later claimed responsibility.
A 23-year-old student of Korean origin went on a rampage at Virginia Tech University in the town of Blacksburg in April 2007.
He killed 27 students and five teachers before committing suicide.
A disturbed 20-year-old man killed his mother in Newtown, Connecticut, in December 2012 before blasting his way into Sandy Hook Elementary School and shooting dead 20 six- and seven-year old children and six adults.
He later committed suicide.
In October 1991 a man shot dead 22 people in a restaurant in the town of Killeen and then killed himself.
California office party
A newlywed radicalised Muslim couple stormed a Christmas office party at a social services centre in San Bernardino in December 2015 and gunned down 14 people, wounding 22 others.
They were shot dead by police.
Fort Hood Military Base
In November 2009 a US army psychiatrist opened fire at his military base in Killeen, killing 13 people and wounding 42, before being overpowered by police.
New York immigrant centre
A Vietnamese immigrant shot dead 13 people at a civic centre in the New York state city of Binghamton in April 2009, before killing himself.
A troubled former serviceman shot randomly at workers at the Washington Navy Yard headquarters in September 2013, killing 12 people before he was shot dead by officers.
A young man wearing body armour stormed a cinema showing a late-night premiere of a Batman film in Aurora in July 2012.
He opened fire and released teargas killing twelve people and injuring 70 others.
He was sentenced to life in prison.
Two teenage boys shot and killed 12 classmates and a teacher at Columbine High School in Littleton, Colorado, in April 1999, before killing themselves.