The shocking video displays a lack of action by police, reports ITV News Correspondent John Ray
Police waited 77 minutes to enter a classroom where a gunman massacred 19 children and two teachers, chilling CCTV from Robb Elementary School in Uvalde, Texas shows.
It also depicts police officers running away from the classroom where the attack happened, as they hear gunfire.
The newly released video has added to the anger over the failed police operation, depicting in devastating clarity the actions of killer Salvador Ramos and slow response of law enforcement.
The footage, posted by local news outlet Austin American-Statesman on its website, shows the 18-year-old gunman crashing his pickup truck and entering the primary school at 11.33am on May 24, carrying a semi-automatic rifle.
The sound of gunfire is then heard for more than two minutes.
The video includes 911 tape of a teacher screaming: “Get down! Get in your rooms! Get in your rooms!”
The camera in the corridor shows that police are on the scene just three minutes later but do not enter the classroom and shoot the gunman dead for another 77.
As the gunman enters the school and makes his way down a corridor, a child who is thought to have been in the toilets can be seen just metres away from the shooter and then running away as shots begin to ring out. The student is reported to have later been rescued from the school.
Minutes later, the actions of the child are replicated by the police.
Two officers approach the classrooms minutes after the gunman enters, then run back to their colleagues who are massing in the corridor amid the sounds of gunfire.
For more than an hour after this, while the gunman is in a classroom filled with unarmed fourth graders (children aged nine and 10), police are seen standing in the corridor awaiting orders as school pupils die just metres away.
As the time passes, more and more police officers arrive on the scene.
By 12.21pm, several officers with tactical gear can be seen approaching the classroom, yet it isn't until 12.50pm that officers finally enter the room and fatally shoot the gunman.
While law enforcement are waiting, a man wearing a vest which reads "sheriff" can be seen using a hand sanitiser dispenser which is affixed to the wall.
The video is a disturbing 80-minute recording of what has been known for weeks now about one of the deadliest school shootings in US history, that heavily armed police officers, some armed with rifles and bulletproof shields, massed in the hallway and waited more than an hour before going inside and stopping the May 24 massacre.
Earlier this month, a report commissioned by the Texas Department of Public Safety found that an Uvalde police officer could have shot Ramos before he entered the school but hesitated while he waited for permission from a supervisor.
The footage released on Tuesday has anguished Uvalde residents anew and redoubled calls in the small South Texas city for accountability and explanations that have been incomplete - and sometimes inaccurate - in the seven weeks since the shooting.
Hours after the video was published, residents at a Uvalde City Council meeting shouted for action and demanded that police face consequences.
The attack in Uvalde was one of the latest in a string of mass shootings across the US that have renewed debate over gun laws and mental health.
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