The Uvalde police waited for reinforcements while the attacker continued to shoot at students and teachers.

Police officers responding to the shooting at an elementary school in Uvalde, Texas, which left 19 students and two teachers dead, waited more than an hour to enter the classroom to neutralize the shooter while waiting for backup to minimize the risk to their officials, according to new videos and other documents reviewed by

.

Officers who responded to Robb Elementary School waited more than an hour to enter the classroom even though they already knew there were victims inside who needed medical attention and that the shooter was still a threat, documents show.

Police also knew that more than a dozen children were still alive.

while the 18-year-old attacker was still entrenched.

New evidence reveals that the operation commander sought to minimize the risk to officers' lives, which led to the decision to wait

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Uvalde Police Chief Peter Arredondo complained about the time it was taking for the bulletproof shields he had requested to enter the campus to arrive, according to recordings seen by The

.

[The chief of the Uvalde school police did not have his radio during the massacre]

"People are going to wonder why we took so long," said a man identified by investigators as Arredondo.

"We are trying to preserve the rest of life," he added.

An official working on the case told the

that they are still trying to determine if any of the fatalities could have been saved, had they received medical care sooner.

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It is known that one of the teachers died in the ambulance and three children died in nearby hospitals.

Arredondo also tried to communicate with the killer through a locked door, but was unsuccessful.

Arredondo was apparently

, having already shot two of them when they tried to approach the room, according to documents reviewed by The

.

Both the state of Texas and the Department of Justice are conducting their own investigations into the Uvalde police response to the massacre, which has been widely criticized for its late response to the attack.