Minutes after being released on bail by Melbourne police, Michael Rawson tried to snatch a two-year-old boy from his father's arms.
He was wearing a dressing gown in the midst of a drug-induced psychosis and said he wanted to give the child a hug, believing it to be his own youngest child.
It was a terrifying experience for the family, County Court Judge Felicity Hampel said.
She described CCTV footage of the November 2019 incident as harrowing.
"What happened was every parent's nightmare - there was determination, force and persistence in your conduct," she said.
"You grabbed the child and wrestled him from his father while he desperately tried to protect him and keep him safe."
Police had picked up 41-year-old Rawson earlier in the day, disoriented and trying to break into cars. He was charged with minor offences and released on bail - sent on his way from Preston police station in a taxi.
But just 150 metres down the road Rawson got out of the car.
Across the road the father and son out walking their dog, paused while the little boy played on a seat.
As the man helped his child off the seat Rawson ran toward them, calling out "I'll help him down".
The man told Rawson not to touch his child, but he grabbed him with both hands and pulled him away.
The father took back his son but Rawson shoved the father into the bushes where they struggled.
Curled up on top of his son, the father was repeatedly punched in the back of the head by Rawson who managed to pull the boy away again.
He tried to run but was stopped by a bystander and the father grabbed the child back.
Rawson took off, trying to get into cars before hiding in the garden of a nearby apartment building, where police arrested him.
He had used ice before the incident and told doctors he used GHB for the first time the night before believing it might help him sleep.
Rawson only fell into substance use and abuse later in life, and had never suffered a psychotic episode before, the judge said.
He pleaded guilty to attempted kidnapping, assaulting the child and his father, and offending while on bail.
He feels a sense of "horror and shame" at his actions which are an incentive for him to remain abstinent upon his release from prison, she said.
Rawson was jailed for four-and-a-half years on Tuesday and must serve a minimum of two years and three months before he's eligible for parole.