Body camera footage captured the moment the Uvalde school police chief repeatedly begged an 18-year-old gunman to put down his weapon after he opened fire in a classroom.

Robb Elementary School Police Chief Peter Arredondo was recorded standing outside the classroom trying to negotiate with Salvador Ramos - rather than engage with the mass shooter, who ultimately never responded to his pleas.

Arredondo urged the teen to talk to him, trying to assure him that 'this could be peaceful' and asking him to 'please put your firearm down'.

Despite his efforts, another round of gunshots was heard from the classroom.

'Can you hear me sir?' Arredondo asked following the shots.

'Sir, if you can hear me, please put your firearm down, sir. We don't want anybody else hurt.' 

Angry parents and community members have called for Arredondo's termination since the May 24 massacre that left 21 dead. 

He was placed on administrative leave last month. 

Uvalde Mayor Don McLaughlin disclosed previously that another on-site negotiator had tried calling Ramos but the gunman never answered the phone.

Meanwhile, the Texas House investigative committee released a preliminary report Sunday revealing officials found 'multiple systemic failures' and poor leadership by law enforcement the day of the shooting.

The newly-released video showed that Arredondo tried to speak with Ramos several times from the school hallway.

During his initial attempt at communication, Arredondo seemed unaware that Ramos had barricaded himself in a classroom with students.

'Let me know if there's any kids in there or anything,' Arredondo pleaded. 'This could be peaceful.'

The officer, met with no response continued: 'Can you tell me your name, anything that can help please?' But, Ramos did not answer.  

Minutes later a 911 dispatcher alerted police that a student had called, revealing children and teachers were trapped with the gunman.

Six minutes later Arredondo is seen trying to open the door to a nearby classroom with a set of keys, but fails to do so. 

He passes the keys off to another officer who does make entry into the room.

Additional officers, who are more heavily armored, arrive on scene but little action appears to be taken.

Then, another round of shots are fired, prompting Arredondo yet again to plead with the shooter.

'Can you hear me sir?' he asked.

'Sir, if you can hear me, please put your firearm down, sir. We don't want anybody else hurt.'

Someone is heard saying 'I know, I know' and another officer says: 'That's what we're doing, we're trying to get him out.'

It was still at least another 30 minutes before police entered the classroom where Ramos had barricaded himself and killed him.