Ballistics experts on Friday reenacted the 2018 shooting rampage at a Parkland high school in South Florida as part of an investigation against a police officer accused of failing to act against the perpetrator of the shooting.

The reenactment occurred at the three-story Marjory Stoneman Douglas High School where Nikolas Cruz shot and killed 14 students and three adults on February 14, 2018.

Experts planned to fire 139 shots with an AR-15 semiautomatic rifle - the same one used by Cruz - while technicians recorded the sound of the live gunfire.

It was unclear if the entire test took place because local reporters barely heard four shots from outside the school.

The aim of the reconstruction was to determine what Scot Peterson, then the security officer at the school, heard during the six-minute rampage.

On that day, Peterson failed to rush into the school after hearing the first shots from Cruz, a former student. Peterson took refuge instead in a nearby building for 48 minutes while he waited for backup.

Peterson, 60, claimed that he did not intervene because he didn't know where the shots were coming from. Relatives of the victims sued him, however, claiming that he fled out of cowardice, shirking his duties and leaving students to die.

In June, a court acquitted the police officer of child neglect charges in the first US criminal trial of an officer accused of inaction during a school shooting.

Friday's reconstruction was part of a civil case against Peterson, in which family members of victims and survivors seek damages.

The Parkland shooting intensified US debate over gun control. Cruz, then 19, legally purchased the gun used at the school, despite having mental health problems.

A court sentenced him last year to life in prison after he was spared the death penalty when a jury could not reach a unanimous verdict.

The building where Cruz killed 17 people and injured 17 others was kept intact until now to allow for police investigations. Local authorities plan to tear it down this year.