The 19 children and two teachers massacred at a south Texas elementary school were in a single fourth-grade classroom where the gunman barricaded himself, authorities said on Wednesday.
Police circled Robb Elementary School in Uvalde, Texas, 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, identified as 18-year-old Salvador Ramos.
Ramos began his rampage by shooting his grandmother, crashing his car then entering the school wearing tactical gear and carrying a rifle, authorities said. His grandmother survived but is in critical condition.
State and federal investigators are still working to determine the gunman's motive, Olivarez told MSNBC. Multiple children were also injured, he told Fox News, though he did not have an exact tally.
The deadliest school shooting in nearly a decade has reignited debate over America's gun laws just days before former president Donald Trump headlines a forum at the National Rifle Association (NRA)’s annual meeting in Houston - just a four-hour drive away.
The attack, which came 10 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, when in God's name we do what we all know in our gut needs to be done," he said, his voice rising in a crescendo.
Biden ordered flags flown at half-staff daily until sunset on Saturday in observance of the tragedy.
"I am sick and tired of it. We have to act," Biden, a Democrat, said, without proposing specific legislation.
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.
Mass shootings in the United States have frequently led to public protests and calls for stricter background checks on gun sales and other firearm controls common in other countries. But such measures have repeatedly failed in the face of strong Republican-led opposition.
Pope Francis on Wednesday said he was "heartbroken" by the shooting and called for an end to "the indiscriminate trafficking of weapons."
Uvalde, a community deep in the state's Hill Country region about 80 miles (130 kilometres) west of San Antonio, has about 16,000 residents, nearly 80 per cent of them Hispanic or Latino, according to US Census data.
"We’re a small community and we need your prayers to get us through this," Hal Harrell, the school district superintendent, told reporters on Tuesday, his voice quaking with emotion.
'Guns flow like water'
In the wake of the shooting, at least two Texas Republican elected officials called for beefing up security at schools and arming teachers, an approach opposed by gun control advocates.
"The reality is that we don't have the resources to have law enforcement at every school," Texas Attorney General Ken Paxton told Fox News on Tuesday. "Nothing is going to work perfectly."
Democratic US Senator Chris Murphy of Connecticut, a leading advocate for legislation to restrict the proliferation of guns, told reporters: "I just don't understand why people here think we're powerless."
"You know, guns flow in this country like water. And that's why we have mass shooting after mass shooting," he said.
The shooting appeared to spur national soul searching, even though the sheer number of such incidents in recent years has numbed many Americans.
Shaken by the events in Texas, NBA coach Steve Kerr refused to talk about basketball at a pre-game news conference on Tuesday and instead called for stricter gun control. "When are we going to do something?" he asked.
Firearms became the leading cause of death for US children and adolescents starting in 2020, surpassing motor vehicle accidents, according to a University of Michigan research letter published in the New England Journal of Medicine last month.
