Uvalde cops ‘didn’t try to open Robb elementary school door for 77 minutes & had chance to shoot gunman who killed 21’

now reportedly shows the cops made no attempt at opening the door between the time Salvador Ramos stormed into the school and shot down pupils and teachers and the time police finally killed him.

Investigators also say the doors might have been unlocked - and Ramos could not have locked the door that connected the classrooms from the inside, according to a law enforcement source.

All the doors at the elementary school are designed to lock automatically once closed and can only be opened with a key from the outside.

The timeline of the tragic events shows at least one of the doors' locking systems might have malfunctioned, as Ramos was able to enter at 11.33am local time through an exit door that a teacher had pulled shut.

Moments later, the footage also shows Ramos was able to open the door to the classroom with his assault-style rifle, showing police may have been to enter that door too.

Authorities are now investigating whether the doors were locked or not - and why police failed to open them, even with a "halligan," a tool similar to a crowbar.

Police initially explained how they had been struggling to find a master key to open all the doors because they thought the doors were all locked.

Embattled Uvalde School District Police Chief Pete Arredondo, who led the response on-scene, insisted all doors were locked and that he had personally searched for a master key during the shooting as he tested a janitor's key ring with 20 to 30 keys attached.

Arredondo's account contradicts the new surveillance footage, which showed no attempt by police to open the doors.

Dramatic photos, meanwhile, showed terrified children being rescued by Uvalde cops after the horror shooting.

While parents and family members waited anxiously outside the school for updates, some children were able to escape through windows with the help of officials.

Border Patrol officials and local police worked together to pull children out through windows and direct them to safety during the shooting.

Uvalde law enforcement officials confirmed that the death toll included 19 students and two teachers.

The shooting is still under investigation, but authorities believe Ramos acted alone.

The shooting became the worst elementary school massacre since Sandy Hook in 2012.

It surpassed the number of dead in the Stoneman Douglas High School shooting, leaving 17 teens dead and 17 others injured on Valentine's Day in 2018.