A school shooting in Texas has claimed the lives of 19 children and two adults, including a teacher and the gunman, while injuring others.
It is the deadliest primary school shooting in the US since Sandy Hook a decade ago.
This is what we know.
How did it unfold?
About 11:30am local time (2:30am AEST) on Tuesday the shooting began at Robb Elementary School, in south-west Texas.
An 18-year-old gunman got out of his car and opened fire at the school.
Erick Estrada, from the Texas Department of Public Safety, told CNN the teenager crashed in a ditch near the school.
He said law enforcement officers saw the gunman, clad in body armour, emerge from the crash carrying a rifle and "engaged" the suspect, who managed to charge into the school and open fire.
Texas governor Greg Abbott said the shooter was likely killed by responding officers but that was still being investigated.
Mr Abbott identified him as 18-year-old Salvador Ramos, and said he had a handgun and possibly a rifle.
Homeland Security assistant secretary of public affairs Marsha Espinosa said Border Patrol agents went to the scene and at least one was wounded.
Uvalde Consolidated Independent School District Chief of Police Pete Arredondo said the gunman acted alone and that the crime scene was "still being worked on".
"Let me assure you the intruder is deceased and [police are] not actively looking for another individual or any other suspects in this case," he said.
A motive for the shooting is not yet known.
What has the President said?
President Joe Biden spoke to the media this morning, saying he was "sick and tired" of the massacres and it was time to act.
"Don't tell me we can't have an impact on this carnage," he said.
He said these kinds of mass shootings "rarely happen anywhere else in the world" and would haunt the children and families.
"See their friends die as if they're on a battlefield, for God's sake. They'll live with it the rest of their lives," he said.
Who are the victims?
Just under 600 children go to Robb Elementary School, which is in a mostly residential neighbourhood, and it covers the second, third and fourth grades.
The exact ages of the victims haven't been made public yet.
It was not immediately clear how many people were injured.
The school is in Uvalde, a town of about 16,000 people between San Antonio and the border with Mexico.
A heavy police presence remains around the school, with officers diverting traffic and FBI agents coming and going from the building.
The shooting happened two days before school was supposed to end for the summer break and the school district's superintendent has cancelled all school activities in the region.
Is it the worst school shooting?
It's the deadliest school shooting in Texan history.
Four years ago, a gunman fatally shot 10 people at Santa Fe High School in the Houston area.
In 2012, a heavily armed gunman killed 26 people, including 20 children between the ages of five and 10, in a rampage at Sandy Hook Elementary School in Connecticut.
The United States experienced 61 "active shooter" incidents last year, the FBI reported this week.
The number of attacks, casualties and geographic distribution has increased from 2021 figures.
Who has said what so far?
Mr Abbott said the gunman "shot and killed horrifically, incomprehensibly," the students and a teacher.
"I want to tell you that what happened in Uvalde is a horrific tragedy that cannot be tolerated in the state of Texas," he said.
Earlier, Mr Biden ordered US flags to be flown at half-mast at the White House and other public buildings "as a mark of respect for the victims", until May 28.
Connecticut senator Chris Murphy, who represented the Sandy Hook area as a congressman, made an emotional plea after the shooting and begged his colleagues to finally pass legislation to address the nation's continuing gun violence problem.
"Find a path forward here. Work with us to find a way to pass laws that make this less likely."
The shooting came days before the National Rifle Association's annual convention was set to begin in Houston.
Mr Abbott and both Texan US senators were among elected Republican officials who were scheduled to speak at a leadership forum sponsored by the NRA's lobbying arm.
Vice-President Kamala Harris said that people normally say in a moment like this, "our hearts break — but our hearts keep getting broken … and our broken hearts are nothing compared to the broken hearts of those families".
"We have to have the courage to take action … to ensure something like this never happens again," she said.
ABC/Wires
