Matthew John Finnie, 43, was sentenced in Newcastle District Court on Thursday to two years and six months in jail for what Judge Tim Gartelmann, SC, said was an act of "serious, unprovoked violence on members of the public".

The court heard that Finnie had a cocktail of drugs in his system, including heroin, speed, Valium and Lyrica, when the attack took place on Glebe Road at Hamilton South on February 3, 2023.

According to a statement of agreed facts, Finnie got on the bus demanding passengers - none of them known to him - give back his bag.

"Where the f*** is my money?" he said to one passenger before he verbally abused a 16-year-old school girl, called her an explicit name, and tried to open her backpack.

When the driver told Finnie to get off the bus, the parolee turned his attention to a man sitting nearby.

Finnie punched him dozens of times in the head and to the body, kneed him repeatedly while holding him in a headlock, and rammed his head into a metal pole.

The entire time, Finnie continued to demand the man return his bag.

Police later found Finnie lying in a nearby carpark and arrested him.

Judge Gartelmann said on Thursday Finnie was in an "irrational mental state" at the time, and was dealing with the resurfacing of severe childhood trauma which had led to substance abuse.

Finnie apologised before his sentence was handed down.

"No-one deserves something like that ... yeah that was pretty horrible," he said from jail at Parklea after footage of the assault was played to the court.

"It must have been pretty terrifying for all of them, not just the victim."

His sentence was backdated to account for time he has spent in custody since he was charged. He will first be eligible for parole in June.