Nikolas Cruz studied the Columbine High School massacre ahead of his own deadly rampage in Parkland, Fla. earlier this year.
The revelation comes from a new commission set up to investigate the Feb. 14 mass shooting at Marjory Stoneman Douglas High School, where Cruz is charged with killing 17 people.
“He mapped it out, he had been planning this for a while,” Pinellas County Sheriff Bob Gualtieri, who chairs the state legislature-created commission, said Tuesday in comments carried by the Sun-Sentinel.
Thirteen people were killed during the April 1999 massacre at Columbine, where two students armed with a trove of guns carried out a planned attack before killing themselves.
It was one of the worst school shootings at the time, prompting a wave of new security standards in schools to deal with a potential gunman.
The new commission’s 20 members, who held their first meeting Tuesday, also watched a rough animation that illustrated how Cruz moved through the school’s freshman building with his legally bought AR-15-style rifle.
A black dot with a line jutting out was meant to denote Cruz, who made his way from the first to third floor in a matter of minutes.
Dots meant to represent his victims turn from green to purple for the people Cruz killed, and to yellow for those who were injured.
Parents of some students killed in the tragedy were rattled to see the crude re-enactment of the children’s last moments.
“I knew which dot was my daughter so it was pretty brutal for me,” Andrew Pollack, a commission member whose daughter Meadow was killed, said to the Sun-Sentinel.
At no point did Cruz make it into a class room, the recording shows, confirming survivor accounts that he shot through doors and windows.
Investigators who presented the video credited teachers’ on the second floor for going into a “Code Red” to lockdown their classrooms, and no one was shot.
Cruz was able to strike several people when he made it to the third floor, however, when the gunsmoke from his rifle set off fire alarms.
Pollack, who lost his daughter, refused to refer to Cruz by name during the hearing, instead using his prison number: 18-19-58.
He questioned why the Broward County Sheriff’s Office hadn’t compiled a full review of Cruz’s infractions leading up to the massacre, asking if it’s "normal, two months after an investigation [started], not to have all his disciplinary records," according to the Miami Herald.
Gualtieri signaled some people weren’t working with the investigation, which will put out a report in January, but threatened to use its subpoena power if necessary.
“We’ve got some hard questions that need to be answered,” he said.
Cruz, who faces 17 murder counts, is due in court Friday for a hearing.