(NewsNation) — Chilling video was released Tuesday showing the inaction of police officers inside Robb Elementary School, as they waited in a hallway for nearly an hour while a gunman massacred 21 people inside a classroom.

The surveillance footage, which was first published by the Austin American Statesman, sparked more outrage from victims’ families and citizens in Uvalde who wonder why more was not done by police to pursue to shooter.

Even police response experts, including retired police officer and officer training expert Rick Smith, were surprised by what they saw in the footage.

“It was very horrific. It was very hard to watch, understanding that we lost 22 souls, 19 children and two teachers. It was very tough to watch,” Smith said Wednesday on NewsNation’s “Rush Hour.”

Smith said the No. 1 priority for officers responding to a scene like the one in Uvalde should be “to stop the killing,” followed by the care and extraction of anyone who might be wounded. To stop the killing, officers must follow “driving forces,” such as gunfire, when they arrive on the scene.

This is where the officers inside Robb Elementary School began to fail, Smith said.

“When the officers first arrive, when the first seven officers arrive, they do exactly that,” Smith said. “Two officers go to the gunfire, they drive to the gunfire, exactly what we’re supposed to do, but then what we see is a loss of momentum.”

The officers Smith is referencing appear to run toward the sound of gunfire when they enter the school, but quickly retreat when that gunfire is directed at them. After the initial retreat, no officer engages the shooter for almost an hour, even though children were still calling 911 from inside the classroom.

“When you look at this from 30,000 feet, they turned this from an active shooter event into a barricaded incident and certainly they failed to realize and understand they still had a driving force and a responsibility to get in there and do some medical aid for those kids,” Smith said.

At an Uvalde City Council meeting Tuesday night, residents were vocally upset over the police officers lack of action in taking down the shooter. Uvalde resident Jesus Rizo echoed the sentiments of Uvalde citizens to NewsNation’s “Prime.”

“It seems like (the shooter) was given a lot of opportunity to basically do whatever he wanted,” Rizo said. “He just kind of strolled on in, took his time, and the police once they came in, they moved toward him but then they just all moved back and we just can’t understand why they would do that.”

Uvalde Mayor Don McLaughlin said, however, that it is too early to decide whether any officers should be taken off the force.

“I don’t know they need to step down,” he said. “But everything needs to be reviewed.”

Rizo said the time has now come for every Uvalde police officer to rethink their decision to be cops and decide if putting on the badge every morning “is really for them.”

“If it’s not for you it’s O.K., we respect your decision to step aside and let somebody else that’s willing to take that job apply for the job,” Rizo said.

Texas Republican Sen. Ted Cruz said the footage was “deeply disturbing” and people needed answers to know “what the hell went wrong.”

“We must have accountability and transparency to understand how these failures could have happened — and to ensure they never happen again,” Cruz said. “The families of those we lost, and the community of Uvalde deserve answers and they deserve accountability.”