Ballistics experts will fire up to 139 shots at Marjory Stoneman Douglas High School on Friday during a reenactment of the 2018 Parkland massacre organized as part of a lawsuit that accuses a sheriff’s deputy of failing in his duty to protect the victims.

As the reenactment takes place, technicians outside a three-story classroom building will record the sound of the gunfire, seeking to capture what the deputy assigned to the school, Scot Peterson, heard during the six-minute attack.

The shooting, which sparked a nationwide movement for gun control, left 17 dead, 17 wounded and hundreds traumatized in the South Florida community. Former Stoneman Douglas student Nikolas Cruz, 24, pleaded guilty in 2021 and was sentenced to life in prison.

Peterson — who worked for the Broward Sheriff’s Office, also targeted in the lawsuit — says he didn’t hear all the shots and couldn’t pinpoint where they were coming from because of echoes. He got within feet of the building’s door and drew his gun, but then backed away and stood next to an adjoining building for 40 minutes, making radio calls. He has said he would have charged into the building if he knew that’s where the shooter was.

Families of the victims bringing the lawsuit contend Peterson knew Cruz’s location, but retreated out of cowardice and in violation of his duty to protect their loved ones.

Peterson, 60, was acquitted in June of felony child neglect and other criminal charges for failing to act, the first U.S. trial in history of a law enforcement officer for conduct during an on-campus shooting.

But the burden of proof is lower in a civil lawsuit. Circuit Judge Carol-Lisa Phillips allowed the test, but made clear she was not ruling on whether the recording will be played at trial. That, she said, will have to be argued later — it is likely Peterson’s attorneys will oppose the attempt. No trial date has been set. The families and wounded are seeking unspecified damages.