Multiple officers were inside Robb Elementary School armed with rifles and at least one ballistic shield by 11:52 a.m. on May 24, but they didn't breach a classroom door and take out the gunman who killed 19 children and two adults for nearly an hour, according to documents reviewed by the Austin-American Statesman. 

The new details shed light on the shifting timeline that law enforcement has provided about the response to the third-deadliest school shooting in U.S. history.

Salvador Ramos, the 18-year-old suspected gunman, walked into the school at 11:33 a.m. then entered a pair of adjoining classrooms and opened fire. 

Three minutes later, 11 officers entered the school. The first officer with a ballistic shield arrived at 11:52 a.m., while two other officers with ballistics shield arrived at 12:03 p.m. and 12:05 p.m., according to the Austin American-Statesman. 

As ballistic shields and additional firepower arrived at the scene, some officers were questioning the plan. According to the Texas Tribune, a special agent with the Texas Department of Public Safety arrived about 20 minutes after the shooting started and immediately asked if there were still children in the classrooms. He then reportedly said: "If there is, then they just need to go in."

Another officer replied that it was unclear if there were any children in the classrooms and the special agent again reiterated the need "to go in there." The special agent was then told that whoever was in charge would determine that, the Tribune reported. The special agent then began to help evacuate other children who were still in the school.

Texas Department of Public Safety Director Steven McCraw previously said that the incident commander, Uvalde school police chief Pete Arredondo, thought that the situation had transitioned from an active shooter to a barricaded subject, and that there was "time to retrieve the keys and wait for a tactical team with the equipment to go ahead and breach the door."

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After police entered the school, the gunman could be heard firing shots inside the classroom at 11:44 a.m. and 12:21 p.m., the Statesman reports. 

Several 911 calls were also made from inside the classroom, including at 12:03, 12:10, 12:13, 12:16, 12:19, and 12:36 p.m.

Eva Mireles, a teacher who died on the way to the hospital after the shooting, called her husband, Uvalde school district police officer Ruben Ruiz, and said that she was wounded

"She says she is shot," Ruiz told officers as he entered the school around 11:48 a.m., according to the body camera transcript reviewed by the New York Times. 

Uvalde robb elementary banner

A banner hangs at a memorial outside Robb Elementary School on Friday, June 3. (AP/Eric Gay)

Officials have also said that law enforcement held back while they tried to find a key to open the classroom door, but San Antonio Express-News reported last week that the classroom door was unlocked and no one ever checked the door before breaching it at 12:50 p.m. and taking out the gunman.

A Halligan bar, an ax-like tool used by firefighters to force open locked doors, was also available if the door had been locked, according to the Texas Tribune.

Officials offered conflicting information on the timeline in the days after the shooting, but have not held any press conferences for weeks. 

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A special House committee investigating the shooting has been questioning law enforcement officials behind closed doors. 

Another committee formed in the Senate will hold a public hearing on Tuesday and Wednesday in which the public and invited speakers will testify on school safety, police training, and social media. 

At the federal level, the Justice Department is also conducting an independent review of law enforcement's response.