Shannon Daniel Norgate befriended the 12-year-old, speaking to him about sex and drugs, before enticing the boy into his unit.
The then 23-year-old exposed himself to the boy before offering money for oral sex, a Queensland Court of Appeal judgment says.
Weeks earlier he was released from prison after admitting to targeting boys at and near a primary school, while dressed in a black shirt with the word "security" on it.
Norgate, then aged 21, encouraged a child walking to school to go into a toilet block near shops then locked him in the cubicle.
He directed the boy to pull his pants down but the child resisted before refusing to return to the toilets.
Days after talking to the principal about enrolling a child at the school Norgate accosted two boys, aged four and five, in the toilet block.
He indecently touched one and pulled down the shorts of the other.
"You were plainly laying in wait, and in a place where you would have anticipated children such as these to come upon that location, and it was only a matter of time, as events revealed, before that occurred," a District Court judge said in sentencing him in March 2020.
He was handed a four=year jail sentence, suspended after serving nearly 14 months in custody.
Weeks after being released Norgate groomed the 12-year-old boy.
He has significant intellectual disabilities and a history of expressing violent attitudes and fantasies during mental assessments, Justice David Boddice states in a Queensland Court of Appeal judgment.
Norgate also has convictions for using a carriage service to menace, harass or cause offence, trespass, wearing uniforms that imitate those of police and possession of weapons.
Sentencing him in April to three years behind bars for the grooming, in addition to the balance of the suspended sentences, a judge described Norgate as "a true predator".
But the court failed to have regard to totality, the Appeal Court found on Friday.
Norgate pleaded guilty to grooming that did not involve physical touching or sexual acts.
"That sentence was outside comparable yardsticks," Justice Boddice said, as the court reduced the sentence to two years behind bars.
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National Sexual Abuse and Redress Support Service 1800 211 028
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