School Shooting At Robb Elementary In Uvalde, Texas
Days after the Uvalde school shooting, multiple schools across the country are receiving threats of shooting and terrorism. In photo: crosses with the names of victims of a school shooting, are pictured at a memorial outside Robb Elementary school, after a gunman killed nineteen children and two teachers, in Uvalde, Texas, U.S. May 26, 2022. Reuters / MARCO BELLO

Desperate parents gathered outside Robb Elementary School and implored police to storm the Texas school as Tuesday's massacre was unfolding, with some fathers having to be restrained, videos that surfaced on Thursday showed.

The videos - along with initial accounts of the shooting timeline from authorities - suggest up to an hour passed between the beginning of the attack and the moment officers breached the classroom where 18-year-old Salvador Ramos had killed 19 children and two teachers. They shot him dead.

The New York Times reported that most, if not all, of the victims in the classroom of 9- and 10-year-old students likely died in the first few minutes of the attack, citing a person familiar with a preliminary timeline compiled by investigators.

A spokesperson for the Texas Department of Public Safety, Chris Olivarez, told CNN that investigators were still trying to confirm a minute-by-minute account, including how long Ramos remained barricaded inside the classroom. The department did not immediately respond to requests for comment on the Times report.

In one video posted on Facebook by a man named Angel Ledezma, parents can be seen breaking through yellow police tape and yelling at officers to go into the building.

"It's already been an hour, and they still can't get all the kids out," Ledezma said in the video. He did not immediately respond to a request for comment.

Another video posted on YouTube showed officers restraining at least one adult. One woman can be heard saying, "Why let the children die? There's shooting in there."

"We got guys going in to get kids," one officer is heard telling the crowd. "They're working."

The massacre - the worst school shooting in nearly a decade - has reignited a national debate over the country's gun laws. President Joe Biden and his fellow Democrats have vowed to push for new restrictions, despite resistance from Republicans.

There were few warning signs: Ramos, a high school dropout, had no criminal record or history of mental illness. Governor Greg Abbott said on Wednesday that Ramos had written an online message to someone minutes before the attack saying he was about to "shoot up an elementary school."

Authorities said Ramos shot his grandmother in the face at the home they shared before fleeing and crashing his car outside the school sometime around 11:30 a.m. (1630 GMT). His grandmother, who is hospitalized in critical condition, managed to call police.

Outside the school, Ramos, armed with an AR-15 semi-automatic rifle, evaded a school police officer, dropping a bag full of ammunition as he did so. Officials have offered conflicting accounts as to whether Ramos and the officer exchanged gunfire before Ramos was able to enter the school.

"We're trying to establish exactly what was his role and how he encountered the shooter," Olivarez told CNN.

Ramos wounded two responding officers inside a hallway before barricading himself inside the classroom, Olivarez said. The attack drew a massive law enforcement response, including hundreds of officers, who encircled the building and broke windows in an effort to evacuate children and staff.

Eventually, members of a U.S. Border Patrol tactical unit breached the classroom and killed Ramos, with one agent wounded in the crossfire, officials said.

The Uvalde Police Department announced the incident was over shortly after 1 p.m. (1800 GMT).

Olivarez said the attack lasted 40 to 60 minutes, though he couldn't say whether that time frame began when Ramos shot his grandmother or when the teenager arrived at the school. The FBI was working on obtaining surveillance video from school cameras.

A fourth-grader who was in the classroom told a CBS affiliate in San Antonio that the gunman began shooting before entering and then came in, crouched down and said, "It's time to die."

The boy, whom the station did not identify, said he hid under a table until police came into the classroom, setting off an exchange of gunfire.

At least 17 people were also injured, including children.

Victims' loved ones took to social media to express anguish over the loss of children who never came home from school.

"We told her we loved her and would pick her up after school," Kimberly Mata-Rubio posted on Facebook in a remembrance of her daughter, Alexandria Aniyah Rubio, a fourth-grade honor student. "We had no idea this was goodbye."

GUN CONTROL DEBATE

The shooting came 10 days after a white supremacist shot 13 people at a supermarket in a mostly Black neighborhood in Buffalo, New York.

In Washington, Democrats and Republicans in the Senate appeared far from any compromise on new gun restrictions.

Biden, who has urged Congress to act, will visit Uvalde, a close-knit community of about 16,000 residents, in the coming days.

The Texas rampage is the deadliest U.S. school shooting since a gunman killed 26 people, including 20 children, at Sandy Hook Elementary School in Connecticut in December 2012.