Slain bikie Mark Easter was a doting father and dearly loved by his partner Biancha Simpson, his friends say.

She was one of the last people to see him alive after having dinner with him in Potts Point on Tuesday night, police say.

He was a high-ranking member of the Rebels bikie gang but friends say they are at a complete loss as to why he was shot dead and dumped on the side of a road on the outskirts of Sydney.

The exact time the 37-year-old disappeared was not known but close friends say they believe he was possibly picked up from his Little Bay home because both his cars were left in the driveway.

Last Friday morning, he was found shot in the head and left on the side of the Pacific Highway at Cowan, near Berowra.

Close friend Angus McGuffie said he was "shattered" his close mate had been killed and wanted him remembered as a loving father, an honest man and fitness fanatic.

"He wasn't afraid to be a dag to make his son laugh - the bond they had was unbreakable. He wasn't a bad person," Mr McGuffie said.

"Anyone who knew Mark wouldn't have one bad word to say about him … every memory I have with [him] is nothing but good times and [his] ridiculous laugh. He welcomed everyone and anyone and treated everyone with respect," he said.

"And I know he loved Biancha Simpson more then anything."

Another close friend told Fairfax Media his death should not be automatically linked to his appointment as Sergeant at Arms of the gang's City chapter.

Mr Easter was formerly a member of the Nomads.

"The bikie scene is not as hard as people as make out. This is the first murder in a while - a lot of bikies don't kill each other these days, they are weak," a friend, who did not wish to be named, said.

"He hasn't been a bikie his whole life; he was a good person, we used to train all the time and hang out and he was a fit man, a good man," he said.

Homicide detectives have set up Strike Force Nevorie to investigate Mr Easter's death and are appealing for anyone with information to contact Crime Stoppers on 1800 333 000.