Desperate pleas for a stop to the gun massacres plaguing the United States rang out Sunday during President Joe Biden's visit to Uvalde, where he prayed for the 19 children and two teachers slain by a teen gunman in the small Texas town.

"Do something!" rang out shouts from a crowd in the street as Biden left Sacred Heart Church where he attended mass with mourning relatives.

Factfile on the shooting at an elementary school in Uvalde, Texas, US, where a teenage gunman killed at least 19 young children and two teachers on Tuesday, May 24. Factfile on the shooting at an elementary school in Uvalde, Texas, US, where a teenage gunman killed at least 19 young children and two teachers on Tuesday, May 24. Photo: AFP / STAFF

"We will. We will," Biden responded to the crowd, before heading to private meetings with relatives of the dead and with first responders.

Biden, accompanied by his wife, Jill Biden, was in Uvalde 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.

The first couple began by visiting a makeshift shrine at Robb Elementary School, where last Tuesday the teen gunman walked in with an AR-15-type semi-automatic and began his slaughter.

A police officer stands near the makeshift memorial for the shooting victims outside Robb Elementary School in Uvalde, Texas, on May 28, 2022 A police officer stands near the makeshift memorial for the shooting victims outside Robb Elementary School in Uvalde, Texas, on May 28, 2022 Photo: AFP / CHANDAN KHANNA

Both wearing black, the Bidens held hands in front of the memorial, walking slowly along the thicket of wreaths, bouquets, white crosses and blown-up photos of the slain children.

Biden, whose adult son Beau died seven years ago this Monday from cancer, and whose first wife and infant daughter perished in a car accident, made the sign of the cross, appearing to wipe away a tear.

An aerial view shows Robb Elementary School and the makeshift memorial (center, Bottom) for the shooting victims in Uvalde, Texas, on May 28, 2022 An aerial view shows Robb Elementary School and the makeshift memorial (center, Bottom) for the shooting victims in Uvalde, Texas, on May 28, 2022 Photo: AFP / CHANDAN KHANNA

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.

"Our hearts are broken," Archbishop Gustavo Garcia-Siller said at the church.

An aerial view shows Robb Elementary School and the makeshift memorial (center, Bottom) for the shooting victims in Uvalde, Texas, on May 28, 2022 An aerial view shows Robb Elementary School and the makeshift memorial (center, Bottom) for the shooting victims in Uvalde, Texas, on May 28, 2022 Photo: AFP / CHANDAN KHANNA

Biden was not scheduled to speak publicly in Texas, but on Saturday he renewed his so-far fruitless call for Congress to overcome years of paralysis to toughen firearms regulations -- especially on weapons like the AR-15.

"We cannot outlaw tragedy, I know, but we can make America safer," Biden said.

US President Joe Biden and First Lady Jill Biden are in the White House but getting the operation running is complex US President Joe Biden and First Lady Jill Biden are in the White House but getting the operation running is complex Photo: POOL / Alex Brandon

Ricardo Garcia, who works at Uvalde's hospital, said he was "honored" Biden came to visit his town, but wanted to see more action on gun control.

The 47-year-old was at work on Tuesday when first responders brought in children from Robb.

"I just can't get out of my mind that screaming in the halls from the moms when they got the bad news," Garcia said. "It's still there. I can't sleep at night."

US President Joe Biden and First Lady Jill Biden are in the White House but getting the operation running is complex US President Joe Biden and First Lady Jill Biden are in the White House but getting the operation running is complex Photo: POOL / Alex Brandon

US President Joe Biden visits a memorial outside of Robb Elementary School in Uvalde, Texas US President Joe Biden visits a memorial outside of Robb Elementary School in Uvalde, Texas Photo: AFP / MANDEL NGAN

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."

Surviving children described 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.

Though his teacher lay on the floor bleeding, she repeatedly told the students, "'Stay calm. Stay where you are. Don't move,'" Daniel told The Washington Post.

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 Congress has repeatedly failed to agree on possible new gun 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.