Officers attached to Orana Mid-Western Police District, operating as part of Strike Force Kerrison, arrested a 58-year-old and 39-year-old at a property 34km south of Wellington early on Friday morning.

Homicide Squad Commander Detective Superintendent Danny Doherty said it was believed there were other involved parties in the killing.

"We're confident that there are other people who were involved in this, and that other people both assisted in the planning of this murder and were present at this murder," Det Sup Doherty said.

"At this stage, we are looking at the 58-year-old man facing charges of murder and the 39-year-old man facing charges of being an accessory to murder, both will also be looking at firearm offences as well."

Mr De Britt was killed on January 14, having suffered a gunshot wound to the head.

Police are canvassing the Stuart Town property for a weapon that can be tied to the killing.

"The investigation relates to a conflict with the Bandidos OMCG, we'll allege that the people we've arrested had links to a criminal group and they were in conflict with Bandidos OMCG," Det. Sup. Doherty said.

"We're confident that there are other people involved in this, there's information that suggests that others assisted in the planning of this murder, that others were present during the murder and were there afterwards assisting."

While the exact nature of the conflict is still under investigation, Det. Sup. Doherty reassured residents in the region

"Since this happened in January, police have been investigating and we haven't seen any retaliatory shootings or any other offences, that's because of the great work by the local police," Det. Sup. Doherty said.

"We believe - and we're hopeful - that there will be further arrests down the track, but we do believe the 58-year-old man was the one who committed the murder."

"Anyone else who was involved should be nervous, they should be looking over their shoulder, because we're following and we're not far behind."

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