"The biggest guy of the group, I'd say he was 6 foot 3, 6 foot 4, and 115kg, came over and king-hit the guy and knocked him out."
The men fled on their bikes before police arrived, leaving the man out cold and other victims "shocked and shaken up".
"It was completely surreal, we were just walking across the park then these guys roll up and just started attacking this guy and yelling. [Then] they went for his girlfriend and she was trying to get out of the way but I saw her get hit at least once in the head."
Mark said that according to the man who was attacked, the gang had approached the couple earlier in the day for drugs.
Police Inspector Barry Smalley said police attended the brawl, which involved at least 10 people and happened at about 6.50pm on Wednesday. He described the offenders as African and said no arrests had been made. An investigation was under way.