New surveillance video obtained and published by the Austin American-Statesman on Tuesday offers a detailed look at how long it took officers to take action when they arrived at the scene of the mass school shooting in Uvalde , Texas, in May.

The footage is around four minutes long and includes several disturbing video clips, including ones of the shooter arriving at Robb Elementary School and walking through the halls with his semiautomatic rifle, the voices of teachers screaming as they urge children to stay in their classrooms and the sounds of gunfire as dozens of officers from various agencies stand by for over an hour before taking any action against the gunman, who ultimately killed 19 children and two teachers.

The full annotated and timestamped video, which the newspaper edited to remove the sounds of children screaming, can be viewed here .

As heard in the footage at 11:31 a.m., a teacher calls 911 to report the shooter, and he fired at the campus from the parking lot.

Get down! Get in your rooms! Get in your rooms! the teacher yells to students while on the phone with 911 operators.

Bystander and surveillance footage captured over the next few minutes shows the gunman entering the building, not noticing a small child hiding as he makes his way down the hallway. The gunman then enters a classroom and fires for two and a half minutes, releasing more than 100 rounds though those moments are not included in the American-Statesmans video.

Several police officers are then seen entering the building at 11:36 a.m. with weapons drawn, with some rushing down the hall and crouching outside classrooms. At 11:37 a.m., the gunman fires shots at some of the officers, who retreat and take cover at the other end of the hallway.

The footage cuts to 11:52 a.m., when more officers arrive, some with ballistic shields. Still, none make an attempt at a rescue.

After nearly 30 minutes pass without police action, the footage records the sounds of the gunman firing four more rounds at 12:21 p.m. Again, no rescue attempt is made.

Its not until 12:50, an hour and 14 minutes after they arrived on the scene, that officers are heard breaking into the classroom and killing the shooter.

It remains unclear, even with the release of the video, what officers were doing during that time. Texas Department of Public Safety Director Steve McCraw has said that the school district police chief erroneously called for the situation to be treated as if the gunman was just barricaded, which requires a slower response process, when they should have treated it as an active shooter situation and responded as quickly as possible.

This video was released hours after Texas state Rep. Dustin Burrows (R) announced that the Texas House committee investigating the school shooting will release videos from the hallway on the day of the shooting to some members of the Uvalde community on Sunday before eventually releasing them publicly.