Students trapped inside a classroom with a gunman repeatedly called 911 during this week’s attack on a Texas elementary school, 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 at 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 at risk, Steven McCraw, the head of the Texas Department of Public Safety, said at a contentious news conference.

“It was the wrong decision,” he said.

Friday’s briefing came after authorities spent three days providing often conflicting and incomplete information about the more than an hour that elapsed between the time Ramos entered the school and when U.S. Border Patrol agents unlocked the classroom door and killed him.

Ramos, who had driven to Robb Elementary School from his home after shooting and wounding his grandmother there, went on to kill 19 children and two teachers in the deadliest U.S. school shooting in nearly a decade.

"He's in room 112," a girl whispered on the phone at 12:03 p.m., more than 45 minutes before a U.S. Border Patrol-led tactical team finally stormed in and ended the siege.

The on-site commander, the chief of the school district's police department in Uvalde, Texas, believed at the time that Ramos was barricaded inside and that children were no longer at immediate risk, giving police time to prepare, McCraw said.

"From the benefit of hindsight where I'm sitting now, of course, it was not the right decision," McCraw said. "It was the wrong decision, period."