U.S. President Joe Biden and first lady Jill Biden visited Uvalde, Texas, Sunday to sympathize with relatives and survivors of the latest mass shooting in the United States, following the killing last week of 19 school children and their two teachers.

The Bidens walked past the floral tributes to the victims outside Robb Elementary School, often pausing to touch the cardboard cutout pictures of each of the 21 victims and read their names.

While the Bidens paid their tributes, the U.S. Justice Department announced that at the request of Uvalde Mayor Don McLaughlin, it would conduct a review of the police response to Tuesday’s attack on the school, “to identify lessons learned and best practices to help first responders prepare for and respond to active shooter events.”

In the Texas shooting, law enforcement officials are being sharply questioned about why it took so long, more than an hour, to confront the gunman.

The president and his wife spent nearly seven hours in the small Southwestern city, talking with those most affected by the carnage that ensued after an 18-year-old gunman burst into a fourth-grade classroom and opened fire. Biden also attended a Catholic Mass and later met with first responders.

It is the second time this month that Biden and the United States have been confronted with a mass killing. He earlier visited Buffalo, in the northeastern state of New York, where a white supremacist opened fire, targeting and killing 10 Black people in a grocery store

In the past few days, Texas law enforcement authorities have changed their accounts of exactly how the Robb Elementary massacre unfolded and their response to it.

Even as children trapped in the classroom with the shooter made urgent emergency calls, pleading with police to rescue them, the incident commander on the scene, the police chief for Uvalde schools, assessed — wrongly, as it turned out — that it was no longer an active shooter incident but rather that the assailant, Salvador Ramos, had barricaded himself in the classroom.

As a result, the incident commander, Pete Arredondo, did not immediately order police officers into the classroom to end the mayhem before more were killed.

Eventually, U.S. Border Patrol agents arrived at the school, burst into the classroom and killed Ramos, a high school dropout who bought two assault rifles earlier this month, a few days after he turned 18.

The head of the Texas Department of Public Safety, Steven McCraw, said Friday that with the benefit of hindsight, "it was the wrong decision" to wait to confront the shooter.

Lawmakers in Washington have long been stalemated over tightening gun purchase laws, with Democrats mostly supporting calls for stricter measures and background checks on gun buyers and Republicans almost universally opposed.

In the aftermath of the Uvalde killings, a bipartisan group of Republican and Democratic senators is meeting to try to determine the scope of what new legislation could win congressional approval.

A longtime gun control proponent, Connecticut Democratic Senator Chris Murphy, told ABC’s “This Week” show Sunday, “We need federal legislation. There are more Republicans interested in talking this time” than after past mass shootings.

Raising the age limit for assault weapons purchases or banning their sale altogether—as was done in the U.S. from 1994 to 2004 — are unlikely to be part of any new legislation. Whether any of the possible changes could have prevented the Texas massacre is questionable since Ramos had no criminal record and had not been flagged for mental health care treatment.

Dozens of people gathered Saturday in Uvalde to mourn and pay homage to the people killed last week.

Twenty-one crosses have been placed around a fountain in the city’s courthouse square, one for each of the 19 fourth-graders who died and their two teachers, Irma Garcia and Eva Mireles. A growing pile of flowers, stuffed animals and messages — “Love you,” “You will be missed” — surrounded the crosses. Dozens of candles burned like small eternal flames.

Pastor Humberto Renovato, 33, who lives in Uvalde, asked everyone to join hands and pray.

The investigation continued Saturday into the time it took for police to confront the gunman.

Some 90 minutes elapsed between the beginning and the end of the deadly shooting. Ramos crashed a pickup into a ditch near the school, entered the building carrying an AR-15-style rifle and a bag of ammunition and was inside the school for 40 minutes to an hour before Border Patrol agents stormed in and killed him.

A man kisses the cross of Layla Salazar at a memorial outside Robb Elementary School to honor the victims killed in this week's school shooting in Uvalde, Texas, May 28, 2022.

Samuel Salinas, 10, said Ramos barged into his fourth-grade classroom and said, “You’re all going to die.”

Then “he just started shooting,” Salinas told ABC News.

Another student, Daniel, whose mother allowed him to speak to The Washington Post, was in a classroom down the hall. He said his teacher, who quickly locked the door and turned out the lights, saved their lives. She was shot twice when the gunman fired through the door’s glass window, Daniel said.

For an hour, he said, the students hid in the dark. The only sounds in the room were hushed sobs and his teacher urging the students to remain quiet.

“Stay calm. Stay where you are. Don’t move,” Daniel recalled her saying.

Daniel told the newspaper that he and his classmates were rescued when police broke the room’s windows and they crawled to safety.

The city’s 911 call center received cries for help from at least two students in the adjoining classrooms where Ramos found his victims, McCraw said earlier this week.

"He's in Room 112," one girl whispered to the 911 operator at 12:03 p.m. local time Tuesday.

She called again at 12:43 p.m., begging the operator to "please send the police now," and again four minutes later.

At 12:51 p.m., a Border Patrol-led tactical team stormed in and ended the siege.

Police have not yet found a motive for the shootings.

Ramos’s mother has asked the school children’s parents for forgiveness. In an interview with Televisa, a CNN affiliate, a soft-spoken Adriana Martinez said in Spanish, “I don’t know what he was thinking. … Forgive me. Forgive my son.” (VOA)

•PHOTO: U.S. President Joe Biden and first lady Jill Biden, who holds a bouquet of 21 white flowers, pay their respects at the Robb Elementary School memorial, where a gunman killed 19 children and two teachers, in Uvalde, Texas, May 29, 2022.

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