The boy also downloaded a guide to making bombs in a home kitchen and sketched a picture of a shrapnel-filled improvised bomb left on a city street and exploding, a jury has heard.
The teen, who cannot be identified for legal reasons, has pleaded not guilty to acts in preparation for a terrorist attack and is facing trial in Brisbane Supreme Court.
The jury on Wednesday heard the teen had wanted a device similar to the bomb used in the United States' deadliest domestic terrorist act.
In 1995, a truck bomb destroyed an Oklahoma City government office building in an attack planned by American anti-government extremist Timothy McVeigh.
Excerpts of the teen's diary were read in court on Wednesday referencing the US bombing that killed 167 people.
"Pipe bombs are cool and all but for the sake of not getting caught again I should do a Timothy McVeigh with a large, lethal and destructive explosive," the teen wrote.
McVeigh was executed in 2001.
The teen filmed himself setting fire to liquids and powders in his backyard and sent the videos to a school friend, Queensland Police's Steven Gibb said.
He allegedly sought the same explosive commonly used by terrorists, including in a suicide bombing outside an Ariana Grande concert in England in 2017 that killed 22 people.
"I went to Woolworths and got (a chemical). Not that I could make good (explosives) with how weak the (chemical) is," the teen wrote in his diary.
The teen had downloaded an explosives manual from al-Qaeda in the Arabian Peninsula, a group proscribed as a terrorist organisation.
The manual was titled "how to make a bomb in the kitchen of your mum", said Detective Sergeant Gibb, a former police counter-terror officer.
The manual instructed on how to build a bomb with a casing that would be "turned to shrapnel flying at high speed" when it exploded, he said.
During a search of the teen's parents' home in September 2024, officers found his diary with a sketch of a household device he labelled as "filled with shrapnel and explosives", the jury heard.
The teen labelled the sketch as being left on Boundary Street and exploding, Det Seg Gibb said.
The jury previously heard Brisbane's Boundary Street was on the route of the city's Labour Day march that usually attracts 20,000 people.
The teen is accused of planning to use pipe bombs packed with nails to attack Liberal Party members and the march to promote beliefs he shared with America's notorious Unabomber.
The jury had earlier been told the teen considered Mr Dutton as a potential target.
Images and memes celebrating the Unabomber - US terrorist Ted Kaczynski - were found on the teen's digital devices, Det Sgt Gibb said.
The teen declared the Unabomber as "the GOAT (Greatest Of All Time)" in a text message to a friend.
He wrote in his diary about having thought for years about carrying out a mass stabbing attack in a shopping centre and was surprised when a similar massacre occurred at Sydney's Bondi Junction.
Under cross-examination by defence barrister Laura Reece, Det Sgt Gibb said the teen had written about having hallucinations.
"I heard voices. They were people from my classes. It was like I was dreaming but I was awake," the teen wrote.
He wrote in his diary of how people likely looked down on him as a "struggling autistic child" and his father took away his digital devices out of concern he was losing touch with reality.
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