A Shepparton man was among a group involved in a violent riot at a youth detention centre where other prisoners were assaulted and prison guards and teachers threatened.

Isaac Hindmarsh, now aged 20, pleaded guilty in Melbourne County Court to violent disorder wearing a face mask, four counts of aggravated burglary, armed robbery, three counts of false imprisonment, two counts of assault, two of producing an intimate image, conduct endangering life, and recklessly causing serious injury.

The riot happened at Malmsbury Youth Detention Centre on October 3, 2023, while Hindmarsh — who was 18 at the time — was serving a sentence.

He was one of 13 co-offenders who armed themselves with improvised weapons, including mop and broom handles they sharpened.

The two-hour rampage started with a staff member being threatened by five in the group that they would kill them if they didn’t hand over keys to a different part of the prison.

During the ordeal, the group targeted other inmates, including one who was stabbed and hit with a pole before some of the group took turns to stomp on his head and stab him.

Hindmarsh kicked him in the head, causing him to fall to the ground, before dragging him into a sitting position and kicking him in the face, while six co-offenders stabbed him with poles.

The same inmate was hit in the head with a fire extinguisher and fell unconscious.

Another inmate lost three teeth, had his nose broken, and had lacerations to the head, face and back, as well as a possible concussion in the attack, before being made to dance naked while he was filmed.

He was also made to parade naked along the fence line of that part of the prison, before being assaulted again and barricaded in the laundry room.

Another inmate was attacked by members of the group, including Hindmarsh, who punched him in the head, before the group made him and another inmate kiss while they filmed and streamed it on an iPad they had stolen during the riot.

Youth justice staff and teachers barricaded themselves in an office and hid in toilets as the group rioted.

The group found some of them and demanded they hand over their keys, radios and swipe passes to different areas of the detention centre.

One of the groups of workers was locked in a building after the rioters had sprayed powder from a fire extinguisher in there.

Another youth justice worker was made to go with members of the group while they opened up areas into other parts of the detention centre, while a teacher who said he would accompany her had a sharpened implement held to his throat, and was also punched by Hindmarsh.

The court was told the riot caused about $40,000 damage to the detention centre.

Judge Amanda Chambers described the incident as “violent and terrorising offending” that was “likely to have a lasting impact on the victims”.

She said the group of offenders all acted together, and as such were charged as a group.

“It is not appropriate to split into single offences,” she said.

“Not one member of the group demonstrated regard to the victims.”

The court heard that there were rising tensions between inmates with different gang affiliations, but that Hindmarsh did not have any gang affiliations when he became part of the rioting group.

Judge Chambers said a victim impact statement from one of the teachers told how she “doesn’t know how she lived through it”, while a youth justice worker “thought her life was going to end that day”.

In delivering her sentence, Judge Chambers spoke of Hindmarsh’s childhood of disadvantage and “profound social deprivation” and she accepted these had “played a significant role” in shaping his personality.

She also said Hindmarsh had a significant intellectual disability, and a forensic psychologist noted borderline personality traits and a substance abuse disorder, and said he had a “level of impulse control well below those of his same age peers”.

Hindmarsh was sentenced to three years and nine months in prison, and must serve two years and three months of his sentence before becoming eligible for parole.

The 370 days he has already served in pre-sentence detention is counted as time already served.

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Saturday, 25th July 2026

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