His sister Trish, who appeared via AVL to read her victim impact statement, said Reardon had imposed a life sentence on the whānau.
"You did not have the right to take his last breath from him. We will suffer the life sentence to the end of our days."
Trish described the armed group who went to the house to steal drugs from Butler, who was a known dealer, as a bunch of "yellow-bellied gang members".
Butler's daughter, who addressed the court with a photograph of her father, said she felt numb and devastated when she heard her father had been killed.
"My whānau and I have been to hell and back," she said, crying.
"I can't find it in my heart to forgive you."
She described Reardon as a waste of space and oxygen.
Justice Cooke said Reardon was a senior member of the gang who had taken a lead role in organising and directing the group during the attack.
At least three firearms, two .22 rifles and a shotgun, had been taken to the house.
The men, who wore balaclavas to cover their faces, forced their way into the house and a firearm was pointed at Butler before Reardon pushed him in the chest with the butt of the shotgun.
Butler's brother Brent entered from another room and attempted to disarm one of the gang members.
During the struggle for the gun two clicks were heard, indicating the firearm had failed to fire, Justice Cooke said.
The gang members then retreated from the house with the Butler brothers in pursuit.
Butler was swinging a mallet at the front passenger in one of the cars, and Brent was knocked unconscious by another from the group.
Shots were then fired from one of the .22 rifles, Justice Cooke said.
"He [Butler] ran, holding his neck and coughing up blood."
Justice Cooke said he adopted a starting point of 10 years' imprisonment for Reardon, whose offending was motivated by alcohol and drug abuse.
After allowing a 35 per cent reduction for Reardon's guilty plea and cultural report, he arrived at a sentence of imprisonment of six years' and six months'.
However, Reardon was already subject to the three strikes legislation, meaning he had to serve any sentence imposed without the possibility of parole.
As Reardon was already serving a four-and-a-half-year sentence for an aggravated robbery, committed five days after Butler was shot and killed, Justice Cooke further reduced his sentence to five years' imprisonment.
The five-year sentence is cumulative on the four and a half years' Reardon is already serving.
Three Black Power members, Dwayne Anson Tewhenua Fore, Kemp Rangitahae Rippon and Daniel Shane Whareaorere, pleaded guilty to manslaughter and were sentenced to jail by Justice Cooke in September 2020.
Justice Cooke suppressed all details of the hearing including the sentences and suppressed his reasons for suppressing the information.
The trio had gone on trial for murder in March but it was abandoned because of Covid-19.
They later pleaded guilty to manslaughter after getting sentencing indications to the lesser charge.
In March 2020, Mark Robert Audain pleaded guilty to attempting to pervert the course of justice.
