Uvalde (United States) (AFP) -
A distraught US President Joe Biden laid flowers and prayed Sunday at the makeshift shrine erected in Uvalde to the 19 children and two teachers murdered by a teen gunman after he stormed their elementary school.
Biden, accompanied by his wife, Jill Biden, was in the small Texas town less than two weeks after making a similar trip to the site of another mass shooting -- this time targeting African Americans in a racist attack -- in Buffalo, New York.
Both wearing black, the first couple held hands in front of a memorial outside Robb Elementary School and walked slowly along the thicket of wreaths, bouquets, white crosses and blown-up photos of the slain children.
Biden, who buried his adult son Beau seven years ago after he died of cancer and also lost his first wife and infant daughter in a car accident, made the sign of the cross, appearing to wipe away a tear.
Reprising the increasingly familiar role of national mourner-in-chief, Biden, 79, then attended a Catholic Mass with local residents, ahead of meeting privately with first responders and grieving relatives of the dead.
'Our hearts are broken,' Archbishop Gustavo Garcia-Siller said at Sacred Heart church, where the Bidens sat at the front and the first lady reached out to lightly touch the hands of several worshippers.
Earlier, the arrival of the Bidens' motorcade at the school was met with applause from a crowd. However, illustrating the tension in the town, there were boos at the appearance of Republican Texas Governor Greg Abbott, who strongly opposes new restrictions on gun ownership.
'We need changes,' shouted one man.
Biden was not scheduled to speak publicly in Texas, but on Saturday he renewed his call for Congress to overcome years of paralysis to toughen firearms regulations -- especially on weapons like the semi-automatic AR-15 that the gunman used in Uvalde.
'We cannot outlaw tragedy, I know, but we can make America safer,' Biden said.
- Justice Department probes police -
Harrowing accounts emerged of the ordeal faced by survivors of Tuesday's attack, where the behavior of the police is under severe scrutiny.
Ten-year-old Samuel Salinas was sitting in his fourth-grade classroom when the shooter, later identified as Salvador Ramos, 18, barged in and announced: 'You're all going to die.'
Then 'he just started shooting,' Salinas told ABC News.
Texas authorities admitted Friday that as many as 19 police officers were in the school hallway for nearly an hour before finally breaching the room and killing Ramos, saying the officers mistakenly thought that he had stopped killing and was now barricaded.
Parents have expressed fury and on Sunday the Justice Department announced an inquiry 'to identify lessons learned and best practices to help first responders prepare.'
Survivors describe making desperate, whispered pleas for help in 911 phone calls while police waited.
Some played dead to avoid drawing the shooter's attention. Eleven-year-old Miah Cerrillo smeared the blood of a dead friend on herself to feign death.
Salinas said he thinks Ramos fired at him, but the bullet struck a chair, sending shrapnel into the boy's leg. 'I played dead so he wouldn't shoot me,' he said.
Another student, Daniel, whose mother would not provide his last name, said he saw Ramos fire through the glass in the classroom door, striking his teacher.
The bullets were 'hot,' he told The Washington Post, and when another bullet ricocheted and struck a fellow student in the nose, he said he could hear the sickening sound.
Though his teacher lay on the floor bleeding, she repeatedly told the students, ''Stay calm. Stay where you are. Don't move,'' Daniel recalled.
- 'Have the courage' -
Vice President Kamala Harris on Saturday attended the funeral of a victim of the Buffalo mass shooting -- Ruth Whitfield, who was among 10 people killed on May 14, allegedly by a self-described white supremacist.
'Congress must have the courage to stand up, once and for all, to the gun lobby and pass reasonable gun safety laws,' Harris tweeted.
The Uvalde shooting was the deadliest school attack since 20 children and six staff were killed at Sandy Hook Elementary School in Newtown, Connecticut in 2012.
But despite the epidemic of mass shootings and ever growing flood of private gun purchases, Congress has repeatedly failed to agree on possible new regulations.
This time might be different, some lawmakers say.
Democratic Connecticut Senator Chris Murphy said Sunday there were 'serious negotiations' underway involving members of both parties.
In Uvalde, Robert Robles, 73, said he was glad Biden had visited to show concern but said the president needs to pass laws restricting powerful military style rifles, like the AR-15, and 'protect these kids.'