"Be advised we have possible - could be firecrackers - I think we have shots fired, possible shots fired", Peterson said.
The surveillance footage shows Peterson outside a school building at that time.
The sheriff's office said in a press release "the video speaks for itself". The video released Thursday did not have sound, but radio transmissions appear to indicate the 32-year veteran deputy was nearly immediately aware the shots were fired inside the building.
Citing "strong public interest", a Broward judge last week ordered public release of the four video clips from the surveillance system at Marjory Stoneman Douglas High.
Investigators say school surveillance video shows Peterson then took up a position near the freshman building - a spot he wouldn't leave until the shootings were over. "After being suspended without pay, Peterson chose to resign and immediately retired rather than face possible termination".
"We want a blend of these two qualities where a person is not overly excitable, not easily offended, but at the same time very competent and very capable", said Petersen.
But in radio transmissions released last week it appears the 32-year veteran deputy knew nearly immediately they were coming from inside the freshman building.
Broward County Sheriff Scott Israel speaks before the start of a CNN town hall meeting in Sunrise, Florida, Feb. 21, 2018.
The statement added that the sheriff's office was unable to discuss more about the investigation because of Florida law. Its release comes as the sheriff's office has faced intense scrutiny for its response to the February 14 shooting as well as how its deputies acted before and after the massacre. He said it confirms that Peterson should have entered the building: that is an almost-universal response in police training after the 1999 Columbine High and 2012 Sandy Hook school shootings.
Broward sheriff's Col. Jack Dale disputed Grollnek's conclusion, saying in a statement that the training Peterson and other deputies take includes live-fire simulations for both single deputy and multiple deputy situations.
Video of what happened inside the school is not being released. Peterson, through an attorney, pushed back at Israel's depictions of his actions, though he has not commented publicly since. In the video, he and another man approach a school door while appearing to talk on a radio, then begin to run in another direction.
Video footage, along with audio dispatch records, show Peterson standing outside.
Broward County Circuit Judge Jeffrey Levenson, in an eight-page order released on Monday, said the videos could be released without imperilling the school's security system or endangering the investigation into the massacre. Barring any last-minute appeals, the release is set for noon Thursday.
Prosecutors are seeking the death penalty for Florida school shooting suspect Nikolas Cruz.