The former student who gunned down 17 people at Marjory Stoneman Douglas High School in Parkland, Florida, recorded his plans on three cellphone videos, saying in one that he would try to kill at least 20 people.

According to newly released transcripts of the videos obtained from a source close to the investigation, Nikolas Cruz details how he will carry out the shooting.

“I’m gonna go take Uber in the afternoon before 2:40 (p.m.). From there I’ll go into — onto school campus, walk up the stairs, unload my bags and get my AR and shoot people down at the man — what is it? — the main courtyard, wait, and people will die,” he says.

Investigators discovered the videos on the gunman’s cellphone, which was taken into evidence after the shooting. The videos are listed on the prosecution’s discovery list. Authorities didn’t say when the videos were recorded.

“He knew what he was doing,” said Andrew Pollack, father of Meadow Pollack, a senior who was killed. Pollack said that Cruz, whom he refers to as “18-1958” (Cruz’s case number), won’t be able to claim at trial that he was insane or that he didn’t know what he was doing. “It’s all premeditated murder.”

Pollack, who had not seen the recordings at the time of his CNN interview, said of the killer: “He was going to be laughing while he was doing it. He laughed in the videos (according to the transcripts).

“And he just planned how he was going floor to floor and shoot these, shoot my daughter, and shot her nine times.”

Pollack said he felt conflicted about the release of the videos. He doesn’t want the shooter to get more publicity, but he believes the recordings are very important evidence.

On February 14, Cruz used an AR-15-style rifle to kill 17 people and wound 17 others.

In the videos, the gunman says he wants to massacre at least 20 people with his semiautomatic rifle and he will become notorious and well-known. He describes himself in one recording as being alone and his life as “meaningless.”

Cruz, a former Stoneman Douglas student, roamed the hallways of the 1200 building on campus February 14 for several minutes, targeting victims huddled in classrooms on the first and second floors, killing 14 students and three school employees in one of the deadliest mass shootings in modern US history.

He confessed to the crimes, police said.

A Broward County grand jury indicted the 19-year-old Cruz in March on 17 counts of premeditated murder in the first degree and 17 counts of attempted murder in the first degree. A judge entered a not-guilty plea on his behalf during his arraignment.

Broward County prosecutors have said they plan to seek the death penalty despite his attorney’s offer of a guilty plea in exchange for a life sentence.

If a jury condemns the gunman to die, it will take years for the execution to be carried out. At age 19, he would be the youngest death row inmate in the state.

Florida has 347 people on death row, and has executed 96 people since 1976. So far this year, the state has executed one person.