A single Robb Elementary School security camera, mounted at the end of a hallway, captured the horror and devastating law enforcement mistakes that unfolded for more than an hour on May 24.

A 77-minute recording from that camera offers an unabridged view of police inaction, among the clearest accounts of what happened before and after 19 fourth graders and two teachers were gunned down in their classrooms. It also is at the center of a political struggle over what public information from that day should be released and by whom.

Viewed by the American-Statesman, part of the USA TODAY Network, the video shows the 18-year-old gunman dressed in all black with a backpack casually walk into a rear entrance of the school carrying the AR-15 he purchased a week earlier after his birthday. At 11:33 a.m., he pauses briefly at a closed classroom door decorated with the words “welcome class” before turning right into the main hall.

He continues to walk uninterrupted down the empty hallway – past a bulletin board and hand sanitizer station mounted on the wall – until he reaches Room 111. The camera shows him turning to his left and unleashing a barrage of gunfire as he advances toward the room. A boy who apparently was in the bathroom is seen peeking around the corner before police later rescue him.

Three minutes after the initial barrage, a group of officers from the Uvalde Police Department and the Uvalde school district moved from two ends of the hall to converge on Rooms 111 and 112, where the gunman was. The video shows them being pushed back by his return fire. 

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For the next hour, the video reveals what experts have called one of the worst police failures in American history. The footage shows officers massed in the hallway, increasingly armed with shields and high-powered weapons, but not entering the classrooms to take down the gunman until 12:52 p.m.

A debate over whether the footage should be released for public viewing has spilled into the open in recent days. Republican Rep. Dustin Burrows, chairman of a Texas House committee investigating the shooting response, and Uvalde Mayor Don McLaughlin are arguing for its release, while Uvalde County District Attorney Christina Mitchell Busbee opposes its disclosure.

Republican Rep. Dustin Burrows chairs a Texas House committee investigating the police response to the mass shooting at an elementary school May 24 in Uvalde, Texas.

Amid a shifting official timeline of the law enforcement response and anger among Uvalde residents over lingering questions about the shooting, it provides an unfiltered view of what transpired.

Busbee’s position was outlined in a letter Friday to Burrows from Freeman Martin, the Texas Department of Public Safety (DPS) deputy director of homeland security operations.

Busbee “has objected to releasing the video and has instructed us not to do so. As the individual with authority to consider whether any criminal prosecution should result from the events in Uvalde, we are guided by her professional judgment regarding the potential impact of releasing the video,” Martin wrote.