A Minnesota teenager planned to "destroy everyone" in a massive attack on his high school and family, according to newly-released police interrogation tapes.

In the tapes, John David LaDue calmly outlined a plot to attack Waseca Junior and Senior High School, where he was an 11th grader. He said he'd "enter [the high school] and throw Molotov cocktails and pipe bombs and destroy everyone. And when the SWAT comes, I would destroy myself."

"I was planning to dispose of my family, too," he told police. "They did nothing wrong. I just wanted as many victims as possible."

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The alleged plot was revealed by authorities in early May after LaDue's arrest the month before.

LaDue, 17, allegedly told authorities that he'd hidden his violent fantasies from everyone, including his father, according to the tapes.

"He thinks I'm just a good kid because I can lie pretty well and persuade him that I'm just ordinary," he told police.

(John LaDue/Facebook)

Police said that underneath his facade, LaDue planned an attack similar to the one at Columbine High School in 1999. They said he stockpiled weapons and posted YouTube videos of himself playing with knives as well as testing homemade explosives.

On April 29, resident Chelsie Schellhas watched LaDue cut through her backyard on his way to a storage facility where police say he had amassed an arsenal. She called 911 and officers soon arrived and found the teen in the storage locker.

"I'm grateful I wondered," she told ABC News after the charges were announced in May. "Who knows what the outcome could've been if I [wasn't] nosey."

LaDue told police he was never bullied, citing a mental illness for his reason behind the plot.

"I have good parents. I live in a good town. I think I'm just really mentally ill and no one's noticed and I've been trying to hide it," he told police.

LaDue has pleaded not guilty to charges of attempted murder.

ABC News' Mara Schiavocampo and Susan Aasen contributed to this story.