As questions grow about why Texas police waited outside while a school shooter massacred children, one official has offered an explanation.
Speaking to CNN on Thursday (local time), Lieutenant Chris Olivarez from the Texas Department of Public Safety says officers were cautious entering the school because "they could have been shot".
Olivarez said multiple officers entered the school and were "taking gunfire". They called for reinforcements while isolating the shooter to one classroom.
"But don't current best practices call for officers to disable a shooter as quickly as possible, regardless of how many officers are actually on-site?" host Wolf Blitzer asked.
"Correct, the active shooter situation, you want to stop the killing, you want to preserve life, but also one thing that, of course, the American people need to understand, is that officers are making entry into this building," Olivarez said.
"They do not know where the gunman is. They are hearing gunshots. They are receiving gunshots. At that point, if they proceeded any further not knowing where the suspect was at, they could have been shot, they could have been killed, and that point that gunman would have had an opportunity to kill other people inside that school.
"So they were able to contain that gunman inside that classroom so he was not able to go to any other portions of the school to commit any other killings."
The clip has gone viral online, with many expressing disbelief at the comment.
"Here come the good guys with guns to save us, who on second thought are actually just going to stand over here and pretend to do some paperwork while your kids get slaughtered," wrote author Adam Jentleson.
"Resign. All of them. Shameful," Daily Beast columnist Wajahat Ali said.
Daily Wire host Matt Walsh wrote: "Yes. That's your job. Your job is to put your life on the line to protect the innocent. If you aren't willing to do it, quit and go work at Walmart."
Salvador Ramos, 18, went on a rampage inside Robb Elementary School in Uvalde on Tuesday, killing 19 young children and two teachers.
He was inside for up to an hour as Swat officers reportedly waited for a staff member to bring a key for the classroom he was barricaded in. He was shot and killed after police finally breached the room.
Horrific footage outside the school captured the anguish of parents screaming and pleading with police officers to "go protect the kids".
One of the disturbing clips, seen nearly two million times by Thursday, shows several parents trying to get past police lines. One woman appeared to be pinned on the ground by an officer, with an onlooker screaming: "What the f**k are you doing to her? Let her go."
Another clip caught even more angry parents confronting officers standing around outside, with the livestreamer saying it had "already been about an hour and they still can't get the kids all out".
"That's f***ing crazy, bro – they're standing all outside [and] there's f***ing kids in there still, man," he said.
One mum yelled at an officer: "You're scared of getting shot? I'll go in without a vest – I will."
Javier Cazares, whose 9-year-old daughter, Jacklyn Cazares, was one of the 19 children shot dead in her fourth-grade classroom, was one of the desperate parents at the scene. He blasted cops as "unprepared".
He recalled hearing gunfire and suggesting to others at the scene: "Let's just rush in because the cops aren't doing anything like they are supposed to."
He also told The Washington Post, "We didn't care about us. We wanted to storm the building. We were saying, 'Let's go', because that is how worried we were, and we wanted to get our babies out."
On Tuesday morning, Ramos first shot his grandmother in the face, before taking her pick-up truck and driving it to the primary school. After crashing the vehicle outside, the 18-year-old, who was carrying an AR-style rifle, then ran towards the building.
The gunman ran down a hallway to two adjoining classrooms and barricaded himself in, Texas Department of Public Safety director Steve McCraw said.
"And that's where the carnage began," McCraw said, with all the victims being in the same room.
He refused to give an exact timeline, only saying that Ramos was inside the school between 40 minutes and an hour before officers shot him dead.
It was the deadliest school shooting since 20 children and six staff members were killed at Sandy Hook school in Newtown, Connecticut in December 2012.
Still, Texas Governor Greg Abbott insisted the school shooting "could have been worse" without the officers' response.
"They showed amazing courage by running toward gunfire for the singular purpose of trying to save lives," Abbott said.
"They were able to save lives," he said, conceding, "Unfortunately, not enough."