Exactly one week after police charged Rebels bikie gang member John Weston with the alleged murder of Laurie Starling, his associate Mark Easter was shot dead in the head and dumped on the side of a highway just outside of Sydney.

Homicide detectives are now investigating if Easter's execution-style death had anything to do with Weston's arrest last week and his connections within the Rebels.

Easter, 37, was the Rebels City chapter's Sergeant at Arms when he was killed.

Detective Inspector Grant Taylor said police were not ruling anything out but certainly looking at Easter's connections within the outlawed bikie gang.

"It's ironic that Weston was locked up last week and soon after this had occurred," Detective Inspector Grant Taylor told Fairfax Media.

"They've certainly been seen together – known associates [Weston and Easter]," he said.

Mr Easter was last seen having dinner with his partner on Tuesday night in Potts Point.

When he failed to come home, his partner reported him missing to police.

On Friday a group of council workers found Mr Easter shot in the head and dumped on the side of the Pacific Highway at Cowan, on the outskirts of northern Sydney.

"We identified him through his tattoos, he was reporting missing that day also so it added up," Detective Inspector Taylor said.

It is not known exactly how long his body had been there but no effort was made to conceal it.

"He was very close to the road, it wasn't well hidden," Detective Inspector Taylor said.

His death on Friday came one week after the president of the Rebels Windsor chapter was arrested for the death of Laurie Starling, a judge of the Summernats car festival.

Police will allege Weston shot Mr Starling in the stomach and left him dead and and slumped over the wheel of a vehicle outside his West Gosford car repair and customisation business, the Chop Shop in July last year.

Police say Mr Starling was caught in the middle of a dispute with another underworld figure.

Strike Force Nevorie has been established by detectives from State Crime Command's Homicide Squad with assistance from Ku-Ring-Gai Local Area Command.

Investigators are keen to speak with anyone who may have knowledge of Mr Easter's movements since Tuesday, June 23.

Anyone with information that may assist detectives is urged to contact Crime Stoppers on 1800 33 3000