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PARKLAND (CBSMiami) – The video is silent but it speaks volumes.

Surveillance cameras at Marjory Stoneman Douglas High School captured the frantic moments on campus just after Nikolas Cruz is accused of entering the freshman building and taking aim at anyone in his path.

School resource officer Scot Peterson is seen reacting to the crisis just seconds after the first reports of shots fired at the school came in to Coral Springs dispatch.

He and others ran for a golf cart and headed out towards the chaos.

As the golf cart approached Building 12, Peterson made his first radio transmission.

“Be advised we have possible, could be firecrackers, I think we have shots fired. Possible shots fired. 1200 building,” Peterson said.

In the upper left corner of the screen you see Peterson and as the shooting continued inside the school, he retreated to a position away from the 1200 building and ordered the area shut down.

“Make sure we, uh, get some units over here. I need to shut down Stoneman Douglas, the intersection,” he said.

Seconds later an unidentified person arrived and spoke with Peterson. Peterson then issued another order.

“Get the school locked down, gentlemen,’ he said.

That other person walked towards Building 12 and then walked back.

(VIDEO: Carey Codd breaks down significant moments in the surveillance video.)

During this period, investigators say Cruz continued his assault throughout the floors of the building even trying unsuccessfully to shoot out a window.

Peterson though remained rooted in his initial position and is never seen approaching the Freshman Building.

About the time Cruz left the building, Peterson made another command.

“Broward, do not approach the 12 or 1300 building. Stay at least 500 feet away at this point,” he said over the BSO radio.

WATCH THE ENTIRE SURVEILLANCE VIDEO HERE (no audio)

Over the ensuing minutes as panicked students and victims fled the building the video shows other officers arriving.

It’s difficult to tell which agency they’re from. But the video does not appear to show Peterson moving from his spot.

Related: Shooter ‘Is By Your Room’: 911 Operator Tells Parkland Teacher

We asked Jeff Bell, President of the BSO Deputy’s Association about the video and Peterson’s actions.

“Disappointment is what I see,” Bell told CBS 4’s Carey Codd. “I see him take a position of cover and he’s more concerned with his own personal safety than he is about those kids being executed inside that school.”

Peterson’s attorney told reporters that Peterson received a call of firecrackers, not gunfire, and believed the shots might be coming from outside.

But Peterson’s radio transmissions reference shots inside the building and Bell believes it’s hard to imagine not knowing where the chaos was coming from.

“If he gets there and he hears this gunshots and those kids screaming inside, things like that, he’s got to get into that building or at least get to the door and try to make entry,” he said.

The video seems to support Sheriff Scott Israel’s contention that Peterson took up a position and never went into the school.

Sheriff Israel said he planned to suspend Peterson without pay but Peterson quit.

We tried to reach Peterson’s attorney for comment on this video but he did not respond to our requests.

The video was released after CBS4 and other media outlets sued for the release of the video, arguing it was important to understand the law enforcement response to the shooting.

The release of the footage comes one day after National Walkout Day, where survivors of the shooting and students nationwide walked out of their classrooms to send a message something needs to change when it comes to school safety and gun laws.

For more on our coverage of the Parkland school shooting, click here.

For those needing counseling, these are just some resources offered by Broward schools: browardschools.com/crisissupport

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)