A patched Highway 61 member who murdered a rival in a drive-by shooting is back behind bars after he rejoined the bikie gang he claimed to have left behind.

Now, just weeks after Murray Arnold Simms was recalled to prison, another man involved in the gangland killing will walk free.

Garth Geoffrey Bucknall will be released on Monday. He too will live in Christchurch.

Both men, along with Matthew Bernard Grant and Dean Waka Nathan, were given life sentences for executing Black Power member Max Shannon 14 years ago.

It was August 2000, and the gangs were at war.

Grant was the Highway 61 leader and Shannon's brother, Tony, was Black Power president.

Tony Shannon has since left the gang, but was angry his brother's killers were being released into the city "where they plotted murder".

Black Power prospects could take retribution once all four were released, as Maori people "don't forget", he said.

"I'm not worried for my life, I'm more worried for theirs. If the two gangs are face to face, with these particular members, it's going to be ugly," Tony Shannon said.

A nightclub clash sparked Max Shannon's murder.

The 25-year-old had just finished rugby league practice and was sitting in his car in Silvester St, Woolston, when he was gunned down.

The car was riddled with bullets.

Simms pleaded guilty to murder. Bucknall, Grant and Nathan were convicted at trial.

The four men's imprisonment was a blow to Highway 61, which was struggling to recruit members. Some have since patched over to the Bandidos.

Simms, 44, was first paroled in late 2012.

He claimed to have ceased all gang connections for 10 years. Yet within a month, he wore his patch and relapsed into drug use, a parole board report said.

Simms was recalled to prison last month, after admitting taking drugs.

Bucknall, 45, has been on a release to work programme since March and had "day leaves" since May.

He had "maintained a very high standard of behaviour whilst in prison", a parole board report said.

Bucknall's release conditions forbid him from taking drugs. His only family support and employment was in Christchurch, The Press understands.

Tony Shannon believed Bucknall, like Simms, would return to the gang and be "idolised" for his role in the murder.

He first planned vengeance for his brother's execution, but after his mothers' death became a Jehovah's Witness and left the gang 11 years ago.

In his eyes, revenge now belonged to God.

The same could not be said for Black Power. Old rivalries were not as strong as they were, but that could change, he said.

"These are gangs. It's not a Boy Scouts club. Maori people, they don't forget. They'll carry a grudge for ages.

"I actually hope nothing happens," Tony Shannon said.

The pain of losing his brother was still raw.

He had the power to send Max Shannon away after the bar fight, while tensions cooled, but never saw it as serious enough to lead to murder.

His brother was "a kind fellow. Giving, loved his children, loved rugby league".

Tony Shannon wanted the Parole Board to split up the killers on their release.

He already dreaded bumping into Bucknall by chance.

"They've done their time, but don't put them back into the same environment where they plotted murder," he said.

Simms will not be seen by the parole board again until next October. Grant is eligible for parole next year.

Nathan, who was caught running a drug operation from his prison cell, will not appear before the Parole Board until 2019 at the earliest.

Gang expert Jarrod Gilbert said leaving a gang was akin to leaving a family, but he did not believe the release of Max Shannon's killers would reignite gang tensions as "a lot of water has gone under the bridge".

- The Press