Florida mass shooter Nikolas Cruz was busy on his phone looking up the music video for "Pumped up Kicks" minutes before he burst into Marjory Stoneman Douglas High School and opened fire, killing 17 people, according to trial testimony.

The penalty trial in Broward County Circuit Court entered its third week Monday and will determine whether Cruz, 23, will be sentenced to life in prison or death for the Feb. 14, 2018, massacre in Parkland.

Jurors Monday were shown Cruz's phone activity as he rode in an Uber to the school to carry out the rampage with an AR-15 hunting rifle. 

The 2010 music video by Foster the People topped charts around the world with its controversial lyrics about a school shooting that some have said glorifies gun violence. "All the other kids with the pumped up kicks, you better run, better run, outrun my gun," the song's chorus goes.

Parkland shooter Nikolas Cruz penalty trial

Marjory Stoneman Douglas High School shooter Nikolas Cruz is shown at the defense table during jury selection in the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida, June 28, 2022.  (Amy Beth Bennett/South Florida Sun-Sentinel via AP, Pool, File)

Cruz, then 19, was also texting two people during the 13-minute Uber ride – including telling a girl he loved her after she wrote, "You're scaring me and I want you to leave me alone." She added, "You know I have a boyfriend, right?"

Uber driver Laura Zecchini testified that she took Cruz to the school that day and thought the large black bag he was carrying was for a guitar. He told her he had a music class on campus.

PARKLAND SCHOOL SHOOTING TRIAL: ‘THINGS ARE ABOUT TO GET BAD,' GUNMAN WARNS STUDENT

Nikolas Cruz wearing a striped shirt in court during jury selection

Marjory Stoneman Douglas High School shooter Nikolas Cruz tucks his sweater in while waiting for prospective jurors to enter the courtroom during jury selection in the penalty trial at the Broward County Courthouse in Fort Lauderdale, Florida, April 26, 2022.  (Amy Beth Bennett/South Florida Sun-Sentinel via AP, Pool)

Minutes later, Cruz stalked the school building with a rifle, spraying several classrooms and hallways with bullets, killing 14 students and three staff members. 

FLORIDA MASS SHOOTER NIKOLAS CRUZ TOLD GUN SHOP OWNER AR-15 WAS FOR HUNTING

Prosecutors have said that he showed his victims no mercy, returning to execute some students who were injured on the ground.

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Cruz, who was expelled the school one year prior to the shooting, pleaded guilty in October to 17 counts of first-degree murder.