Officers called in to stop a mass shooting at Robb Elementary in Uvalde, Texas on May 24 delayed confronting the gunman for 77 minutes, despite supervisors being aware that some of the people trapped with the shooter needed medical attention, according to The New York Times, who reviewed video footage and other material documenting the event. According to the investigation, the police waited for protective equipment to lower the risk for the officers involved.

The gunman killed 19 children and two teachers. He was 18 years old and had recently purchased an AR-style rifle.

The school district police chief who reportedly served as command, Pete Arredondo, looked to be “agonizing” over the time it was taking to get shields to protect the officers before they entered the classrooms, per the Times.

Arredondo and others at the scene were aware that some of the people inside the classrooms were still alive, per the documents. More than a dozen of the 33 children and three teachers originally in the classrooms were not dead during the 77 minutes before four officers breached the classrooms.

“People are going to ask why we’re taking so long,” a man who investigators believe to be Chief Arredondo could be heard saying, according to a transcript of officers’ body camera footage via The Times. “We’re trying to preserve the rest of the life.”

Investigators have been examining the events to determine if any of those who died could have been saved had they received medical attention sooner, a source told The Times. It is clear, per the paper’s examination, that some of the victims were still alive and needed immediate medical care: One teacher died in an ambulance, and three children died at hospitals.

Ten-year-old Xavier Lopez was one of the students who died after being rushed to a hospital. “He could had been saved,” his grandfather Leonard Sandoval told the publication. “The police did not go in for more than an hour. He bled out.”

According a transcript The Times obtained, the person believed to be Arredondo acknowledged there were injured people on the scene. “We think there are some injuries in there,” the man believed to be Chief Arredondo said several minutes before the breach, according to the transcript. “And so you know what we did, we cleared off the rest of the building so we wouldn’t have any more, besides what’s already in there, obviously.”

It is unclear at what point Arredondo and other officers on the scene became aware that there were victims that were still alive, but injured. It is also unclear whether any of the officials were aware of the 911 calls made from a child who revealed some people were shot, but still alive.

According to The Times, Arredondo futilely attempted to communicate with the gunman through the classroom doors. After two officers who approached the door were shot at and grazed, Arredondo appeared to have made the decision that breaching the classrooms without protection might lead to officers being killed and so he instead worked on removing other children from the school while waiting for protective gear.

The law enforcement response is under investigation by the Texas state police as well as the U.S. Justice Department, following conflicting reports, and scrutiny over the police’s handling of the events continues to intensify.