Biden grieves with Texas town after latest US school shooting

US president Joe Biden landed in the Texas town of Uvalde on Sunday to comfort families ripped apart by the worst US school shooting in a decade as the public demands answers about why local police failed to act swiftly.

There was mounting anger over the decision by local law enforcement agencies in Uvalde to allow the shooter to remain in a classroom for nearly an hour while officers waited in the hallway and children inside the room made panicked 911 calls for help.

Biden will meet with victims' families, survivors and first responders, attend a church service and visit a memorial erected at the Robb Elementary School where the gunman killed 19 students and two teachers.

Julian Moreno, who was attending Sunday services at Primera Iglesia Bautista where he previously served as pastor, said the police had made “a huge mistake” but that he did not hold it against them.

"I feel sorry for them because they have to live with that mistake of just standing by," Moreno, whose great-granddaughter was among those killed in Tuesday's shooting, told Reuters.

Police say the gunman, 18-year-old Salvador Ramos, entered the school with an AR-15 semi-automatic rifle after earlier killing his grandmother at the house they shared.

Official accounts of how police responded to the shooting have flip-flopped wildly, with calls mounting for an independent probe.

Biden, a Democrat, has repeatedly called for major changes to America's gun laws but has been powerless to stop mass shootings or convince Republicans that stricter controls could stem the carnage.

The Texas visit is his third presidential trip to a mass shooting site, including earlier this month when he visited Buffalo, New York, after a gunman killed 10 Black people in a Saturday afternoon attack at a grocery store.

The Uvalde shooting has once again put gun control at the top of the nation's agenda, months ahead of the November midterm elections, with supporters of stronger gun laws arguing that the latest bloodshed represents a tipping point.

"The president has a real opportunity. The country is desperately asking for a leader to stop the slaughter from gun violence," said Igor Volsky, executive director of Guns Down America.

Vice president Kamala Harris called for a ban on assault-style weapons during a trip to Buffalo on Saturday, saying that in the wake of the two back-to-back mass shootings such arms are "a weapon of war" with "no place in a civil society."

White House aides and close allies say Biden is unlikely to wade into specific policy proposals or take executive action to crack down on firearms because that could disrupt delicate negotiations in the divided Senate.

Senate Democrats have also dialed down the rhetoric as negotiations continued during the chamber's Memorial Day holiday recess this week.

"We've got to be realistic about what we can achieve," Senate Judiciary Chairman Dick Durbin told CNN's "State of the Union" program on Sunday. Durbin's fellow Democrats narrowly control the 50-50 split Senate but need 60 votes to pass most legislation.

Leading Republicans like US Senator Ted Cruz of Texas and former president Donald Trump have rejected calls for new gun control measures and instead suggested investing in mental health care or tightening school security.

Texas Governor Greg Abbott, a Republican, denied that newly enacted Texas gun laws, including a controversial measure removing licensing requirements for carrying a concealed weapon, were relevant to Tuesday's bloodshed and instead also pointed to mental illness.

Ramos, a high school dropout, had no criminal record and no history of mental illness but did post threatening messages on social media ahead of the shooting.