The shooting in Las Vegas has left 59 people dead and more than 525 injured, and is the deadliest mass shooting in recent US history.
The attack took place shortly after 10pm Sunday local time.
Police identified the gunman as Stephen Paddock, 64, who lived in a retirement community in Nevada.
He was armed with more than 10 rifles and fired a barrage from the 32nd floor of the Mandalay Bay Hotel, before killing himself.
The attack in Las Vegas was just the latest mass shooting in the United States. Many recent shootings have been perpetrated by a lone gunman.
The United States government defines as "active shooter" incidents: "an individual actively engaged in killing or attempting to kill people".
- Last month, a man shot and killed five people at a shopping centre in Washington state.
- In June this year, a man fired from his warehouse job in April returned to his old workplace in Florida and shot dead five people before killing himself.
- While in January 2017, a gunman believed to be an Iraq war veteran opened fire at Fort Lauderdale's international airport, killing five people and wounding eight before being taken into custody.
- The second deadliest mass shooting in modern US history was in June 2016, when gunman Omar Mateen killed 49 people and injured dozens more at a gay nightclub in Orlando, Florida before being shot dead by police.
- In 2015, a white man who, after his arrest, confessed to wanting to start a "race war" shot dead nine black people at a church in Charleston in the State of South Carolina.
- Also in 2015, a man and woman opened fire at a holiday party of the man's co-workers in San Bernadino in California, killing 14 people and wounding 21 in what appeared to be a planned attack.
- A man entered an elementary school in Newtown, Connecticut in December 2012, shooting 20 children and six adults. All of the children were aged six or seven and most were girls.