Ten people have been killed in a shooting at a school in Texas.
Officials have said the alleged gunman has been arrested and charged in connection with the incident at Santa Fe High School.
President Donald Trump expressed his "sadness and heartbreak" following the attack.
It comes months after one of America's most deadly shootings at a school in Florida.
Each massacre reopens the debate on America's gun problem, though nothing seems to change.
Here is a look back at some of the deadliest gun attacks at schools and universities in the US in recent history.
Marjory Stoneman Douglas High School, 2018: 17 killed
The Florida massacre is one of the deadliest school shootings in US history.
It was the 18th gun incident at a school in America when it happened in February this year and, according to monitor Gun Violence Archive, the 30th mass shooting in the country.
President Donald Trump condemned the attack in Parkland, saying "no child, teacher or anyone else should ever feel unsafe in an American school".
Virginia Tech University, 2007: 32 killed
The Virginia Tech massacre, which happened on 16 April 2007, was America's worst university shooting, with both students and teachers among the dead.
Seung Hui Cho, 23, was armed with two handguns and hundreds of rounds of ammunition.
The South Korean-born student chained and locked several main doors in the building and went from room to room shooting people.
After massacring his victims, he killed himself.
It was later revealed Cho had a history of mental health problems and had spent time in a psychiatric hospital.
"It was the worst day of violence on a college campus in American history" – George W Bush
Sandy Hook Elementary School, 2012: 26 killed
Adam Lanza, 20, stole his mother's guns after shooting and killing her at their home in Newtown, Connecticut on 14 December 2012.
He drove her car to Sandy Hook Elementary School, where he went as a child.
He killed 20 children, six adults and himself within 11 minutes.
President Obama wiped away tears as he addressed the press following the tragedy.
Even though the massacre led to proposed changes to gun laws, and changes were made in certain states, attempts at federal legislation all failed.
"This evening, Michelle and I will do what I know every parent in America will do, which is hug our children a little tighter and we'll tell them that we love them, and we'll remind each other how deeply we love one another. But there are families in Connecticut who cannot do that tonight" – Barack Obama
Columbine High School, 1999: 13 killed
Eric Harris and Dylan Klebold attacked Columbine High School in Colorado on 20 April 1999.
They murdered 12 students and one teacher and planted more than 100 explosive devices around the school.
They exchanged fire with police officers at the scene before shooting and killing themselves.
Police said Harris and Klebold walked into the school cafeteria and left two bags of explosives which they set to explode.
They left the building and waited, but went back in when they failed to detonate and began their killing spree.
"To the families who have lost their loved ones, to the parents who have lost their beloved children, to the wounded children and their families, to the people of the community of Littleton, I can only say tonight that the prayers of the American people are with you" – Bill Clinton
University of Texas, 1966: 15 killed
Charles Whitman shot and killed 15 people from the viewing platform of the main University of Texas building on 1 August 1966.
A former Marine sharpshooter, the 25-year-old architectural student was able to accurately aim at people below.
He had shot and killed his mother and stabbed his wife to death the night before, before shooting and killing 14 people on this day of his carefully planned attack.
The 15th victim, David Gunby, died in 2001 due to chronic kidney problems which he suffered as a result of the gunshot wound inflicted by Whitman.
One of his victims was an unborn child.
The University of Texas tower stayed closed for 25 years.
"What happened is not without a lesson: that we must press urgently for the legislation now pending in Congress to help prevent the wrong person from obtaining firearms" – Lyndon B Johnson
Umpqua Community College, 2015: Nine killed
Chris Harper-Mercer, 26, died in an exchange of gunfire with police in Oregon after he shot and killed nine people at Umpqua Community College in Roseburg, Oregon on 1 October 2015.
He had body armour and was armed with three pistols, a rifle and five rounds of extra ammunition.
He was said to have supported the IRA and admire a man who shot and killed a TV presenter live on air.
His victims were an assistant professor and eight students.
"There's been another mass shooting in America… As I said just a few months ago, and I said a few months before that, and I said each time we see one of these mass shootings, our thoughts and prayers are not enough. It's not enough" – Barack Obama
Isla Vista, 2014: Six killed
British-born student Elliot Rodger killed six people in a gun and knife rampage near the campus of University of California, Santa Barbara, on 23 May 2014.
The 22-year-old "repeatedly stabbed" three men to death in his apartment before taking to the streets in his BMW to target female students.
He had three semi-automatic handguns and 400 rounds of ammunition with him when he died from a self-inflicted gunshot wound.
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In a disturbing 141-page document entitled My Twisted World, as well as in YouTube videos, Rodger had vented his rage at women who rejected him.
"I will punish all females for the crime of depriving me of sex," he wrote.
"All died much too young but it's important that we do not let the arithmetic of this atrocity define them" – University of California president Janet Napolitano
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