A man was assaulting his associate in an act of retribution when the impact of his attack knocked over a toolbox, revealing a hammer.
Hoani Check had forced his victim to the ground, punched him in the face up to 20 times and kicked him in the head.
Check picked the hammer up in his rage and bashed the victim with it up to six times, again in the head, causing lacerations, bruising and swelling.
At a sentence indication in Whanganui District Court in June, Judge Garry Barkle said that Check and the complainant were at a Whanganui address on April 6, 2018.
"Apparently, you approached the complainant to shake his hand concerning a fight between the two of you the previous day," Judge Barkle said.
"Either at or around that time, you then started punching the complainant repeatedly causing him to fall to the floor."
During the assault, Check stood over his associate, punching him with both fists at full-force and kicking him several times in the head.
"In the melee some shelves that were nearby were knocked around.
"A toolbox fell onto the floor, a hammer came out of that toolbox and then you picked up the hammer and hit the complainant in the head approximately four to six times."
Two women that were in the area ran to a neighbouring property seeking help.
The victim suffered from concussion, swelling and lacerations that required stitches and staples.
He was concerned about financial loss as he could not work during his recovery and regarded the assault as traumatising and confusing.
Check appeared before Judge Barbara Morris for sentencing on a charge of wounding with intent to do grievous bodily harm in Whanganui District Court on Wednesday.
Lawyer for the defence Stephen Ross said that his client had a history of struggles with mental health.
"He has been on the mental health act for some time. However, the management of his mental health is complicated by his significant drug history as well," Ross said.
"He was clearly exposed to significant drug use at a young age from others around him that should have known better or were probably in a similar position to him."
In sentencing Check, Judge Morris acknowledged his willingness to engage in restorative justice, his upbringing and his desire to treat his addiction issues.
She also noted his early guilty plea and the remorse he had shown for his actions.
Judge Morris sentenced Check to three years and six months' imprisonment.
"You've paid your price to the victim. You've paid your price to the community. You can't change your past, but you can now look to the future," the Judge said.
"Grab every opportunity while you're in prison to take up alcohol and drug counselling. That will be very important for you Mr Check to ensure you're never standing behind the dock again."