Gun experts will fire live bullets inside a Florida school in a re-enactment of a 2018 mass shooting as part of a lawsuit.

Family of the Marjory Stoneman Douglas High School victims in Parkland are suing an armed school security officer who stayed outside during the attack.

Shots fired inside the school will be recorded outside in order to assess whether the officer heard the gunfire.

The building is scheduled to be torn down in the coming months.

The 14 February 2018 attack is one of the deadliest school shootings in US history. Seventeen people died and 17 others were injured.

School office Scot Peterson, who worked for the Broward Sheriff’s Office, is now being sued for failing to protect the children in a civil case brought by parents.

Video shows how the armed school security officer lingered outside the building, never entering, as he made calls to other police agencies.

In June, a jury in a criminal trial cleared Mr Peterson of 11 charges including felony child neglect, culpable negligence and perjury.

It was the first time in the US that a criminal trial has been held for a school security officer for their actions during a mass shooting.

Mr Peterson has testified that he could not hear some of the shots, and could not identify where they were being fired. He later said he would have acted differently if he knew where the attack was occurring in the three-story building.

On Friday, experts will use the same high-calibre rifle used by the gunman to fire some 140 live bullets into a safety device from the same part of the building where the attack unfolded.

The burden of proof is lower in civil cases, although the judge leading the case has not yet decided whether the audio evidence gathered on Friday will be admissible at trial.

The school campus is closed for summer break, and community members have been warned about the re-enactment.

Ahead of the exercise, a group of lawmakers from Congress toured the site, which has been largely untouched since the attack.

Bloodstains, broken glass, bullet holes and Valentine’s Day cards litter the building, according to reporters who have been inside.

Mr Peterson will be on location for the re-enactment, but will not be taking part.

His lawyer, Michael Piper, told Reuters that multiple witnesses have testified in his criminal case that they thought they heard shots coming from all over the campus.

Relatives of victims are now staging “a video and audio-recorded, choreographed re-enactment to counter the testimony of the people who were there that day”, he said.

Max Schachter, whose 14-year-old son Alex died in the attack, is attending the tour and re-enactment.

He said in a news conference on Friday that he hopes the visit by lawmakers will encourage them to act to prevent further school shootings, CNN reported.

“I’m scared. I’m nervous,” he said ahead of the simulation.

“And obviously I’m going to be here, and it’s going to just remind me what Alex was going through, what all of the victims were going through.”

“It’s going to be scary, but we hope the re-enactment will get a jury to understand that there is no possible way that the school resource deputy only heard two or three shots when 70 went off in that building.”

The gunman, who was 19 at the time of the attack, pleaded guilty last year and was sentenced to life in prison without the possibility of parole.