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

The gunman who killed 19 children and two teachers at a South Texas elementary school was able to enter without any confrontation, authorities said on Thursday, contradicting earlier reports that a police officer engaged him outside the building.

Salvador Ramos, 18, crashed his pickup truck outside the school at 11:28 a.m. (1628 GMT) on Tuesday, fired several shots at two bystanders across the street and walked into the school at 11:40 a.m. (1640 GMT), Victor Escalon, a spokesman for the Texas Department of Public Safety, told a news conference.

Escalon said officers arrived and entered the school four minutes later but took cover after Ramos fired multiple rounds at them and barricaded himself in a fourth-grade classroom, where he shot his victims.

An hour passed before a U.S. Border Patrol tactical team breached the classroom and killed Ramos, Escalon confirmed.

The newly detailed timeline came hours after videos emerged showing desperate parents outside Robb Elementary School during the attack, imploring officers maintaining a perimeter to storm the building, with some fathers having to be restrained.

"That's a tough question," Escalon said when asked if officers should have gone in sooner, adding that authorities would offer more information as the investigation proceeds.

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.