Active shooter response protocols call for police officers to immediately attack and neutralize a gunman – especially when children are the targets – according to experienced law enforcement experts.

But although officers on scene at the Robb Elementary School in Uvalde, Texas, arrived within minutes of the attack on May 24, they posted up down the hallway.

Images from inside the school show that the officers on scene had long guns and body armor, as well as ballistic shields. But they stacked up down the hallway and did not breach the classroom, where the gunman who killed 19 children and two adults holed up.

Children inside the elementary school classroom called 911 multiple times pleading for help. 

UVALDE CLASSROOM DOOR UNLOCKED DURING SHOOTING AS OFFICERS WAITED FOR KEYS: ‘ABJECT FAILURE’

Steve McCraw testifies about Uvalde school shooting

Texas Department of Public Safety Director Steve McCraw testifies at a Texas Senate hearing relating to last month's mass shooting at Robb Elementary School in Uvalde, Tuesday, June 21, 2022, in Austin, Texas. Two teachers and 19 students were killed.  (AP Photo/Eric Gay)

But it wasn’t until 77 minutes after the 18-year-old killer entered the school that a tactical team breached the classroom door and shot him dead, according to authorities. That was far too long, experts say.

"If you attack the shooter, you disrupt the shooter’s plan, and the shooter has to defend himself," Dave Katz, a former special agent with the U.S. Drug Enforcement Administration and now the CEO of Global Security Group, told Fox News Digital. "And if the shooter is shooting at you, that is better than having the shooter attack children."

Based on the images from inside the school, he said it appeared as though the officers had inadequate Level IIIA ballistic shields, which are designed to protect only against common pistol rounds, and based on their formation in the hallway, insufficient training. Katz said his expertise includes being a master shield instructor and leading the DEA’s shield program in the 1990s.

"Those were the wrong shields for the operation," he said. "Those guys had the wrong equipment and the wrong training."

More robust Level III shields would have protected the officers, he said, but even without them, they should have attacked the gunman.

"The moment those kids are in danger, the shields go down, you advance down the hallway, and if you’re shot at, shoot back," said Katz, a father of three. "If you go down, the next guy will get him."

UVALDE SHOOTING: TEXAS DPS OFFICIALS BRING ROBB ELEMENTARY SCHOOL DOOR INTO STATE CAPITOL AHEAD OF HEARING

He said police should train to react quickly and aggressively and warned that schools should have their exterior doors locked at all times

Texas Department of Public Safety Director Steve McCraw told the state Senate’s Special Committee to Protect All Texans last week that the police response to the active shooting was an "abject failure and antithetical to everything we’ve learned over the last two decades since the Columbine massacre."

He said that the first officers on scene had sufficient numbers and firearms to have stopped the gunman within three minutes.

At least one DPS special agent appeared bothered by the lack of action being taken at the scene, according to the updated timeline released by law enforcement. 

"If there's kids in there, we need to go in there," a DPS special agent repeated twice at 11:56 a.m. An unknown officer responded, "Whoever is in charge will determine that." 

"The only thing stopping the hallway of dedicated officers from entering room 111 and 112 was the on-scene commander, who decided to place the lives of officers before the lives of children," McCraw said at the hearing. "The officers had weapons; the children had none. The officers had body armor; the children had none. The officers had training; the subject had none."

More than 10 officers entered the school less than three minutes into the shooting, McCraw said previously, but the incident commander, Uvalde school Police Chief Pete Arredondo, allegedly held up their advance.

Uvalde police chief Pete Arredondo speaks at a press conference in Uvalde

Uvalde Police Chief Pete Arredondo speaks at a press conference following the shooting at Robb Elementary School in Uvalde, Texas, U.S., May 24, 2022.  (Mikala Compton/USA TODAY NETWORK via REUTERS)

Arredondo ordered the officers to wait for more tactical gear and a key to unlock the classroom door, McCraw said. Investigators later determined that the door was likely unlocked. 

McCraw said it was "plain and simple" that there was insufficient training, and he accused Arredondo of making "terrible decisions" as well as delaying officers from other agencies who wanted to move in on the suspect.

Arredondo did not respond to Fox News Digital’s request for comment.

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"The bottom line is no one was in charge," said Katherine Schweit, a former FBI special agent who launched the bureau’s active shooter program. 

She said the response was out of sync with how police train for active shooter crises.

"I believe in the police chief’s first interview, he said, ‘I wasn’t in charge,’ and now we’re hearing he was in charge," she told Fox News Digital. "The bottom line is no one was in charge."

Uvalde's town square memorial grows daily

Crosses with flowers are dedicated to each of the victims of the Uvalde mass shooting. People bring flowers, stuffed animals and cards to the town square memorial one month later.  (Ashley Soriano/Fox News)

Active shooter response policy, which Schweit helped formulate in the wake of the Sandy Hook shooting in 2012, involves directly pursuing the suspect, then neutralizing him, she said.

"We learned from Columbine that we had to do a more effective job of getting in to get to where the shooter was, not just to stop the shooting, but also to look for opportunities to save people who might be injured and bleeding out," she said. 

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That also means moving in, whether officers have ballistic shields or not, and regardless of whether they’re of the appropriate level.

"Everybody wants to have the best, safest equipment, that’s great," she said, "But no active shooter training requires ballistic shields."

Training requires officers to "pursue the shooter, period," she said. And if they had, the uncertainty about the door lock wouldn’t have even mattered. 

"The key situation is one more item that’s showing us that the officers did not execute on the training they received," she told Fox News Digital. "If they had gone after the shooter, they would have gone through the door and found out it was unlocked."

She also stressed that schools need to put emphasis on the "run" in the slogan, "run, hide, fight." The word comes first for a reason.

"The first thing you should consider is to run and/or escape the area," she said. "We are telling teachers and children to stand still and hope that somebody else can come and save them. And I'll tell you, in situations where children have run from school, they have survived."

She also questioned the wisdom of having a small school police department.

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"Would they be better served to consolidate departments to provide bigger and stronger training?" she asked. "Joint training is not the same as having every individual on your team able to do what we needed them to do in Uvalde. They just don’t have the resources, the timing, the training, the depth in those departments."

At the least, she said, smaller departments should consider working closely with larger neighbors or contracting with county agencies.

Congress and the Justice Department are reviewing the Uvalde response

Fox News’ Paul Best contributed to this report.