The gunman who killed 19 children and two teachers at a Texas elementary school barricaded them in a single classroom, authorities said.
Details continue to emerge about yesterday's school shooting - the deadliest US school shooting in a decade, which has reignited debate over gun laws.
The Texas gunman, identified as 18-year-old Salvador Ramos, posted on Facebook that he was going to shoot up an elementary school about 15 minutes before his rampage, Governor Greg Abbott has said.
He also posted a message saying he was going to shoot his grandmother, as well as another one confirming that he had done so, Governor Abbott said.
Ramos entered Robb Elementary School in Uvalde, Texas through a backdoor carrying an assault-style rifle and wearing tactical gear.
During the shooting, police circled the school, breaking windows in an effort to evacuate children and staff, Texas Department of Public Safety spokesperson Chris Olivarez told CNN.
Officers eventually breached the classroom and killed the gunman.
Ramos began his rampage by shooting his grandmother at the home where he lived with his grandparents. She survived but is in critical condition, and investigators hope she can shed light on a motive for the shooting.
Governor Abbott said Ramos did not appear to have any criminal record or history of mental health problems.
A further 17 people suffered non-life-threatening injuries.
The Texas rampage stands as the deadliest school shooting since a gunman killed 26 people, including 20 children, at Sandy Hook Elementary School in Connecticut in December 2012.
My little love is now flying high with the angels above
Uvalde, a community deep in the state's Hill Country region about 130km west of San Antonio, has about 16,000 residents, nearly 80% of them Hispanic or Latino, according to US Census data.
The town was quiet this morning aside from a heavy law enforcement and media presence.
Community members set up fundraisers for the families of the victims to cover funeral costs, while some relatives mourned their losses on social media.
"My little love is now flying high with the angels above," Angel Garza, whose daughter, Amerie Jo Garza, was killed, wrote on Facebook.
"Please don't take a second for granted. Hug your family. Tell them you love them."
The two staff members killed were identified as Eva Mireles and Irma Garcia, fourth-grade teachers trapped in the classroom with their students when the shooting began.
"My best friend, my twin was taken from me," Ms Mireles' daughter, Adalynn Ruiz, wrote on Facebook.
"Thank you for loving me in the best ways and for raising me to become so strong. Everyone who knows you knows how outgoing and funny you were and I will miss your laugh forever."
The gunman, Salvador Ramos, purchased two rifles and hundreds of rounds of ammunition days before the attack, CNN reported, citing a state senator who had been briefed by law enforcement.
Texas Governor Greg Abbott told a news conference this afternoon that Ramos had posted on Facebook that he was going to shoot up an elementary school about 15 minutes before his attack.
Ramos also posted a message saying he was going to shoot his grandmother, as well as another one confirming that he had done so, Mr Abbott said.
He said the Facebook posts were the only advance warning of the rampage, adding that Ramos did not appear to have any criminal record or history of mental health problems.
Facebook rapidly released a statement after Mr Abbott's comments, saying the posts "were private one-to-one text messages that were discovered after the terrible tragedy occurred".
"We are closely cooperating with law enforcement in their ongoing investigation," said Andy Stone, spokesman for Facebook's parent company Meta.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
The attack, which came ten days after an avowed white supremacist shot 13 people at a supermarket in a mostly Black neighbourhood of Buffalo, prompted President Joe Biden to call for stricter gun safety laws in a prime-time address to the American people.
"As a nation, we have to ask when in God's name we're going to stand up to the gun lobby," he said, his voice rising.
But new legislation appeared unlikely to pass in Washington.
Virtually all Republicans in Congress oppose new gun restrictions, citing the US Constitution's guarantee of a right to bear arms, and there was no sign the massacre would alter that position.
White House officials were planning a trip to Texas for Mr Biden, a senior administration official said.
World leaders expressed shock and sympathy. Pope Francis said he was "heartbroken" and called for an end to "the indiscriminate trafficking of weapons".
'Guns flow like water'
Democrats in Washington have renewed calls for stronger gun safety laws.
US Senator Chris Murphy of Connecticut, a leading advocate on the issue, told reporters: "You know, guns flow in this country like water. And that's why we have mass shooting after mass shooting."
The Democratic-controlled US House of Representatives last year passed two bills expanding background checks on firearm purchases. But the legislation has not advanced in the Senate, where at least 10 Republican votes are needed.
In the wake of the shooting, some Republicans called for beefing up security at schools and arming teachers, an approach opposed by gun control advocates.
"There's certainly more we can do to protect the schools by providing law enforcement," Texas Attorney General Ken Paxton told Fox News.
The shooting took place days before the National Rifle Association, the gun industry's main lobbying group, was to hold its annual meeting in Houston.
Several prominent Texas Republicans, including Governor Abbott and US senators Ted Cruz and John Cornyn, were scheduled to speak to attendees.
The nonprofit Gun Violence Archive, which tracks mass shootings, has counted more than 200 so far this year, defined as those in which four or more people were killed or injured.
In Texas, which has some of the country's most permissive gun laws, a gunman killed 26 people at a church in Sutherland Springs in 2017.
A mass shooting killed 10 people at a Houston-area high school the next year, while 23 people died at a Walmart in El Paso in a 2019 attack motivated by racial hatred.
