The Texas school police chief criticised for his actions during one of the deadliest classroom shootings in US history has said that he did not consider himself the person in charge as the massacre unfolded, and assumed someone else had taken control of the law enforcement response.

Pete Arredondo, the police chief of the Uvalde school district, also told the Texas Tribune that he intentionally left behind both his police and campus radios before entering Robb Elementary School.

An 18-year-old gunman killed 19 children and two teachers behind a locked classroom door that the chief said was reinforced with a steel jamb and could not be kicked in.

Poor radio communication is among the concerns raised about how police handled the May 24 shooting and why they did not confront the gunman for more than an hour, even as anguished parents outside the school urged officers to go in.

Separately, The New York Times reported that documents show police waited for protective equipment as they delayed entering the campus, while they became aware that some victims needed medical treatment.

Mr Arredondo told the Tribune that from the hallway of the school he used his mobile phone to call for tactical gear, a sniper and keys to get inside the classroom.

He said he held back from the door for 40 minutes to avoid provoking gunfire and tried dozens of keys brought to him, but that, one by one, they failed to work.

"Each time I tried a key I was just praying," he told the Tribune.

In the weeks since the shooting, Mr Arredondo's actions have come under scrutiny from both state officials and experts trained in mass shooting responses.

Steven McCraw, the head of the Texas department of public safety, has said the school police chief, who he described as the incident commander, made the "wrong decision" to not order officers to breach the classroom more quickly to confront the gunman.

But Mr Arredondo, who told the Tribune he believed that carrying radios would slow him down as he entered the school and that he knew that radios did not work in some school buildings, said he never considered himself the scene's incident commander, and did not give any instruction that police should not attempt to breach the building.

"I didn't issue any orders," Mr Arredondo said. "I called for assistance and asked for an extraction tool to open the door."

His account and records obtained by the Times were published on Thursday as law enforcement and state officials have struggled to present an accurate timeline and details.

They have also made frequent corrections to previous statements, and no information about the police response has been formally released by investigators since the attack.

According to documents obtained by the Times, a man who investigators believe to be Mr Arredondo could be heard on body camera footage talking about how much time was passing.

"People are going to ask why we're taking so long," said the man, according to a transcript of officers' body camera footage obtained by the newspaper. "We're trying to preserve the rest of the life."

Sixty officers had assembled on the scene by the time four officers entered, according to the report.

The two classrooms where the shooting took place held 33 children and three teachers.

Not all the victims were found dead when officers finally went inside: one teacher died in an ambulance and three children died at nearby hospitals, according to the records obtained by the Times, which included a review of law enforcement documents and video that have been gathered as part of the investigation.

The family of Xavier Lopez, 10, said the boy had been shot in the back and lost a lot of blood as he waited for medical attention.

"He could have been saved," Leonard Sandoval, the boy's grandfather, told the newspaper. "The police did not go in for more than an hour. He bled out."

The records obtained by the Times offered other new details, including that the gunman, Salvador Ramos, had a "hellfire" trigger device meant to allow a semiautomatic AR-15-style rifle to be fired more like an automatic weapon, but did not appear to have used it during the attack.

Ramos had spent more than 6,000 dollars (£4,800) amassing an arsenal of weapons that included two AR-15-style rifles, accessories and hundreds of rounds of ammunition, according to the documents.

Eva Mireles, one of the teachers who was killed, made a phone call to her husband, a Uvalde school district police officer, during the attack.

The documents obtained by the Times show that Ruben Ruiz informed responders on the scene that his wife was still alive in one of the classrooms.

"She says she is shot," Mr Ruiz could be heard telling other officers as he arrived inside the school at 11.48am, according to the body camera transcript obtained by the Times.

By 12.46pm, Mr Arredondo seemed to give his approval for officers to enter the room, the Times reported.

"If y'all are ready to do it, you do it," he said, according to the transcript.