During this week's attack on a Texas elementary school, students trapped inside a classroom with a gunman repeatedly called 911, including one who pleaded, "Please send the police now," as officers waited more than an hour to breach the classroom after following the gunman into the building, authorities said Friday.

The commander on the scene in Uvalde — the school district's police chief — believed that 18-year-old gunman Salvador Ramos was barricaded inside adjoining classrooms at Robb Elementary School and that children were no longer in danger, Texas Department of Public Safety Director Steven McCraw said at a contentious news conference.

“It was the wrong decision,” he said.

Police were late more than an hour

Authorities had spent three days giving often contradictory and misleading information about the more than an hour that occurred between Ramos entering the school and US Border Patrol agents unlocking the classroom door and shooting him.

Within two minutes, three police officers followed Ramos into the premises. Within the next half hour, up to 19 officers crowded into the hallway outside. However, it took another 47 minutes for the Border Patrol tactical unit to get through the door, according to McCraw.

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As the gunman opened fire on students, law enforcement personnel from other agencies pleaded with the school police chief to allow them to go in because children were in danger, according to two law enforcement officials.

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According to one of the authorities, audio recordings from the site show other agencies' officers warning the school police chief that the gunman was still active and that the priority was to stop him.

Inside the room, Ramos murdered 19 children and two teachers. Authorities stated his motivation remained unknown.

No answer

Throughout the attack, teachers and children repeatedly called 911 asking for help, including the girl who pleaded for the police, McCraw said.

Young survivors of the attack said they pretended to be dead while waiting for help.

Miah Cerrillo, 11, told CNN that she faked her death by covering herself in a friend's blood. She could hear screaming, more shooting, and music being blared by the shooter after he moved into an adjacent room. Samuel Salinas, 10, who also pretended to be dead, told ABC's "Good Morning America" that the attacker shot instructor Irma Garcia before opening fire on the children.

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Questions have mounted over the amount of time it took officers to enter the school to confront the gunman.

Ramos' Ford pickup smashed into a ditch behind the low-slung Texas school at 11:28 am Tuesday, and the driver rushed out with an AR-15-style gun. Authorities said Ramos entered the school five minutes later and made his way to the fourth-grade classroom, where he executed the 21 victims.

Police killed Ramos at about 12:50 pm, according to McCraw, when bullets could be heard over a 911 call from a person inside the classroom as authorities invaded the room.

An odd time frame

What occurred during that period, in a working-class community on the outskirts of Uvalde, has stoked public outrage and scrutiny of police enforcement's response to Tuesday's assault.

Ramos was still inside when the first US Marshals Service deputies arrived at 12:10 pm. They had hurried to the school from Del Rio, a border town roughly 70 miles (113 kilometers) away, the agency said in a tweet Friday.

But the commander inside the building, Pete Arredondo, the school district's police chief, determined the group should wait to confront the gunman because the scene was no longer an active attack, McCraw said.

The crisis ended at 12:50 pm, when officers used janitor keys to open the classroom door, entered the room, and fatally shot Ramos, he claimed.