Shocking new details about police delay in Uvalde, Texas school shooting have been revealed in a report on Thursday, weeks after 19 children and two teachers were killed in the tragedy.

According to The New York Times report, more than a dozen of the 33 children and three teachers were still alive in the one hour and 17 minutes between when the shooting started, and officers eventually entered to take down the gunman, Salvador Ramos.

Independent reported that the 33 children and three teachers were inside the two classrooms of Robb Elementary School targeted by Ramos.

An official with the knowledge of the investigation told the Times that investigators are currently working to determine whether any of the victims could have been saved if they had received medical aid earlier.

It was still unclear when officers were exactly made aware that the victims in the Texas school shooting needed aid.

However, Uvalde school district police chief Pete Arredondo's voice was heard in body camera footage several minutes before officers breached the school, saying they think they were already some injuries, so they cleared off the rest of the building to avoid more people being hurt.

The report also revealed that the Texas school shooting gunman had a "hellfire" trigger device enabling his semi-automatic rifle to fire like an automatic rifle. Arredondo also learned about the shooter's identity while in school and tried to talk with him through a door.

The Texas Department of Public Safety has referred questions regarding the incident to District Attorney Christina Mitchell, who is coordinating the investigation with the Texas Rangers. The U.S. Department of Justice is also investigating the botched police response.

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Uvalde, Texas School Shooting Police Delay: Officers Admit Failures in Their Operations

The report came more than a week after Texas Department of Public Safety Director Steve McCraw admitted that the Texas school shooting had a series of failures, including the delay in breaching the classroom.

In a news conference late last month, McCraw said the delay in breaching the classroom where the shooter stayed "was the wrong decision" and "there's no excuse for that." He added that "there were children in that classroom that were still at risk, NBC News reported.

McCraw said as many as 19 police officers stood in a hallway outside of the classrooms during the shooting for more than 45 minutes before agents used a master key to open a door and confront the gunman.

He noted that the school district's police chief believed at the time that there "was no more threat to the children" and they "had time to organize" since Ramos was barricaded in a classroom.

"Of course, it was not the right decision. But I wasn't there... I'm just telling you from what we know, we believe there should have been an entry at that... as soon as you can," McCraw said.

McCraw also revealed that the gunman entered the school through the back door he found propped open at 11:33 a.m. and started shooting in classrooms 111 and 112. He noted that at least 100 shots were fired "based on the audio evidence at that time."

Two minutes later, three police officers entered the same door Ramos did. By 12:03 p.m., there were nearly 20 officers in the hallway, McCraw said. However, it was not until 12:50 p.m. that the classroom the gunman was shooting in was breached using a janitor's key.

McCraw noted that the school district's police chief wrongly believed that the incident had changed from an active shooting to a situation where the suspect stopped firing and no longer posed a threat to children.

McCraw said the police chief thought there was time to retrieve the keys and wait for a tactical team with the equipment to go ahead and breach the door to take on the suspect.

The Customs and Border Protection's tactical team reportedly arrived on the scene at 12:15 p.m. but did not breach the classroom until 35 minutes later at 12:50 p.m.

McCraw said there may have been a belief that the incident commander thought there was no one alive inside the classrooms. However, 911 calls from students and teachers revealed they were still in grave danger. It seemed that the information did not reach the officers on the ground.

A timeline of 911 calls provided by law enforcement revealed that at least nine calls were placed between the time the gunman arrived and his death.

Texas Governor Greg Abbott claimed that he was also misled about the initial reports of the police, adding that the officers should explain what happened with "100 percent accuracy" to the public and the victims, who were devastated.

Uvalde, Texas School Shooting

At least 19 children and two teachers died after the 18-year-old gunman entered Robb Elementary School and opened fire with an AR-15 style rifle on May 24.

Tactical officers killed Salvador Ramos during a shootout in a classroom after he went on a killing spree at the Texas school.

On Monday, Abbott penned a letter to Advanced Law Enforcement Rapid Response Training executive director Dr. Pete Blair to help train the school law enforcement to respond to active shooter situations.

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This article is owned by Latin Post.

Written by: Joshua Summers

WATCH: Texas Police Face Anger for Delay in Tackling School Gunman - From  BBC News