FORT LAUDERDALE, Fla. (CBSNewYork) – The interrogation of confessed school shooter Nikolas Cruz lasted for hours.

The 19-year-old former student is accused of killing 17 people during a shooting rampage at Marjory Stoneman Douglas High School in Parkland, Fla., on Feb. 14.

On new video, Cruz appears well aware of being on camera: He mimes shooting himself, he punches himself and he talks to himself.

“At the end you’re nothing but worthless (expletive) dude,” he mutters. “You deserve to die.”

He also tells Broward County Sheriff’s detective John Curcio about hearing a persistent voice or demon in his head.

“What’s the voice telling you?” asks Curcio.

“To hurt people,” replied Cruz.

But for Ryan Petty, the video is more than just another piece in the investigation of Cruz. His daughter Alaina died in the Parkland shooting.

He says the video and what Cruz reveals is also a teaching moment for the community. Despite talk of voices and demons, he feels the video shows Cruz was well aware of his actions.

“What I saw was a shooter trying to come to grips I think with what he had just done,” he said.

MORE: Florida School Shooting Coverage Archive

Fred Guttenberg, whose daughter Jamie died in the shooting, said he has no interest in watching the video.

“I don’t need to see him pour out his thought process,” he said. “He did it. He planned it.”

Gutttenberg pointed to cellphone videos Cruz filmed prior to the shooting as proof of premeditation.

For Guttenberg, the critical issue is bigger than Cruz speaking to law enforcement after 17 people were murdered and 17 others wounded.

“Law enforcement, the school district, the FBI, the mental health community, people around him socially — everybody knew he was a threat to those around him, and there was no law in place to keep him from buying the weapon,” he said.

Now Guttenberg says he is working hard to try and change that system to prevent such a massacre from happening again.

The FBI has admitted it failed to follow up on a tip given about Cruz being a threat, saying “protocol was not followed.

Earlier this year, police released chilling cellphone videos in which Cruz calmly and clearly announced his intention to become the next school shooter, aiming to kill at least 20 people and saying “you’re all going to die.”

The videos are undated, but on one he says, “Today is the day. Today it all begins. The day of my massacre shall begin.”

“When you see me on the news, you’ll all know who I am,” he says in another and then laughs. “You’re all going to die. … Can’t wait.”

In a second video, Cruz briefly discusses logistics, including that he will take Uber to campus about 2:40. He then says he’ll walk onto campus, go up some stairs, open his bag to take out his weapon and start firing. School surveillance video shows that was almost exactly what he did —the only difference being that he arrived at the school at 2:19 p.m.

In the third video, the camera apparently pointed at pavement, he talks about his loneliness, anger and hatred, and announces that the “day of my massacre shall begin.”

“I live a lone life. I live in seclusion and solitude. I hate everyone and everything. But the power of my AR you will all know who I am. I had enough of being told what to do and when to do,” he says. “I had enough of being told what to do and when to do. I had enough of being told that I’m an idiot and a dumbass. You’re all stupid and brainwashed by the political and government programs.”

He also referenced a former girlfriend, saying “I hope to see you in the afterlife.”

Cruz is charged with 17 counts of murder and 17 counts of attempted murder in the attack. His lawyers have repeatedly said Cruz would plead guilty if guaranteed a sentence of life without parole, but prosecutors refuse to waive the death penalty.

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