He helped the man call the police. He was concerned crime in South Dunedin seemed to be growing, and he thought the high price of cigarettes was partly to blame.
"I just care about the nearby neighbourhood," he said.
He would support seeing CCTV cameras on every street corner, he said. The victim of the assault suffered cuts to his head and was taken to Dunedin Hospital for assessment.
He has since been discharged.
One of the offenders was thought to be a Polynesian or Maori man wearing a black hoodie and black beanie, but no descriptions were available for the other men.
In a second attack police believe could be linked, a man was punched in the face while walking along Macandrew Rd in South Dunedin about 8pm.
A group of men punched the man in the head while shouting at him, before driving off in a blue Subaru.
In an unrelated attack, a woman was hit with a wine bottle and had her handbag stolen at the corner of Bay View and Prince Albert Rds just before 9.30pm on Saturday. The victim phoned police saying she had been attacked while drinking with a group.
Police arrived at the scene and a short time later the woman's bag was recovered.
A 17-year-old Dunedin woman was arrested and will appear in the Dunedin District Court on March 30 charged with robbery.