Shannon was found guilty of causing grievous bodily harm following a jury trial in September 2012.
The attack on August 13, 2011, happened at Shannon's 17th birthday party.
The 16-year-old victim suffered third-degree burns to his back, neck, shoulders and face.
He ran from Shannon's house after tearing his T-shirt off and rode home on his bicycle before being taken to Hawke's Bay Hospital for treatment.
Three other teenagers allegedly involved in the incident were not charged as Shannon told the jury at his trial he could not be certain they were the ones who held the victim down.
When being sentenced to three years' imprisonment, Shannon was told he had ruined a young man's life. The physical damage to the victim, had healed but the emotional and psychological damage had not.
Shannon appeared before the parole board twice after being jailed.
He was denied an early release at the second hearing in June last year, as at that stage the board felt he may still pose a risk.
It did however, acknowledge that Shannon had completed a six-month drug treatment programme and had gained confidence and regained self-esteem.
He had been dependant on cannabis at the time of the incident, he told the board, and now had plans in place to deal with his drug problem.
The board noted that Shannon had taken responsibility for his offending although kept him detained until his third hearing, which was last November.
He was released on December 1 with conditions to his sentence having an expiry date of September 11, 2015.
Shannon impressed the board at this progress hearing last month. Panel convenor Alan Ritchie said Shannon was complying and was appreciating the privilege of parole.
Part of the conditions of his parole included no consumption of alcohol or illicit drugs, to be assessed for and directed to attend and complete an appropriate drug and alcohol programme, to notify his probation officer about his residence and employment movements and to not have any contact directly or indirectly with the victim of his offending, unless he had prior written consent from his probation officer.
Because of his progress, his curfew was removed. Mr Ritchie said he felt the board did not have to see him again.
Police wanted to hear from anyone who knew Shannon's whereabouts. They should contact police on 831 0815 or leave information anonymously on Crimestoppers 0800 555 111.
