The worst mass shootings in US history

Agence France-Presse
A man helps a girl to put hand prints on a makeshift memorial on the ground near the Pulse gay nightclub in Orlando, Florida, June 12, 2016. The sign reads, "Today our hearts cry out in unity."
Carlo Allegri

A shooting spree by a heavily armed man at a gay nightclub in Orlando, Florida early Sunday left 50 people dead, making it the worst mass shooting in US history.

News on the Orlando attack is still developing, but President Barack Obama has already declared it "an act of terror, and an act of hate." 

Watch live updates via NBC News:

Here are some of the other major attacks the United States has experienced.

The worst mass shootings in America

-- Orlando, Florida, June 12, 2016: Fifty people die and another 53 are injured when a heavily-armed gunman opens fire and seizes hostages at a gay nightclub.

-- Blacksburg, Virginia, April 16, 2007: A 23-year-old student of Korean origin goes on a rampage at Virginia Tech University, killing 32 people before committing suicide.

-- Newtown, Connecticut, December 14 2012: A young man kills 26 people, including 20 children at Sandy Hook elementary school. He also fatally shoots his mother. He commits suicide.

-- Killeen, Texas, October 16, 1991: A man shoots dead 22 people in a restaurant and then kills himself. Another wounded victim dies later.

US President Barack Obama wipes away tears while talking about Sandy Hook and other mass shootings during an event held to announce new gun control measures at the White House on Jan. 5, 2016.

Other gun attacks that have marked US history

-- Littleton, Colorado, April 20, 1999: Two teenage boys shoot and kill 12 classmates and a teacher at Columbine High School before killing themselves.

-- Aurora, Colorado, July 20, 2012: A man kills 12 people and injures 70 more when he opens fire at a movie theater showing a late-night premiere of a Batman film in a suburb of Denver. The gunman James Holmes is given a life jail sentence with no chance of parole.

-- Fort Hood, Texas, November 5, 2009. US army psychiatrist Major Nidal Hasan opens fire at his military base, killing 13 people and wounding 42, before being overpowered by police. The shooting was the worst such incident on a military base in the United States.