The Parkland school shooter cradled his head in his hands during his penalty hearing as the court listened to graphic witness audio of the shooting

• A jury will soon decide whether or not to give the Parkland shooter the death penalty.
• The shooter pleaded guilty in October 2021 to all 34 charges in the deadly 2018 mass shooting.

Harrowing witness audio of the deadly 2018 massacre at Marjory Stoneman Douglas High School played in the courtroom of the shooter's penalty trial prompted a Parkland survivor to cry at the stand and some to leave the room entirely.

Nikolas Cruz, 23, pleaded guilty in October 2021 to all 17 counts of premeditated murder and 17 counts of attempted murder in connection to the February 2018 mass shooting, where he killed 17 students and staffers and injured another 17 people.

On Monday, opening arguments began in the penalty phase of the shooter's trial, which is expected to take several months. A jury will decide if the gunman will be sentenced to death, or life in prison without the possibility of parole.

During the trial, Parkland survivor Danielle Gilbert, who was a junior at the time of the shooting, took to the stand, giving harrowing testimony of her account of the shooting. She recorded graphic video of the scene, during which children can be heard screaming and gunshots ringing out.

The audio of the witness video was heard by the gallery while the jury could watch the video, according to Cathy Russon, executive producer of the Law & Crime Network, which carried a livestream of the hearing.

In a livestream, the shooter could be seen burying his head into his hands as the audio was played in the courtroom.

Warning: Gunshots and yelling can be heard in the clip.

—Cathy Russon (@cathyrusson) July 18, 2022

Gilbert was in one of the classrooms where the gunman opened fire, killing one student and injuring three, according to her testimony. She said she felt like they were "sitting ducks" in the classroom.

Melisa McNeill, a defense attorney for the shooter, asked for a mistrial after the audio of one the videos was played for the gallery, citing an outburst from the parent of Helena Ramsay, who was killed in the shooting, yelling to "shut it off" over the loud audio.

Broward County Circuit Judge Elizabeth Scherer, who is presiding over the trial, denied the motion, saying it was "not even close to grounds for a mistrial."

During the trial, lead prosecutor Mike Satz described the school shooting as a "planned, systematic ... mass murder," saying that seventy shots were fired on the first floor.

"Three days before the massacre, Cruz made a video saying, 'My name is Nik. I'm going to be the next school shooter of 2018. My goal is at least 20 people with an AR-15 and some tracer rounds. It's gonna be a big event and when you see me on the news you'll know who I am. You're all gonna die. ... I can't wait,'" Satz said in his opening statement.