Several men then continue to punch the unconscious victim, and kick him in the head, before turning on his 23-year-old girlfriend.Police say the attack, at a bar in Elizabeth St in Melbourne's CBD early on January 11, appears to have been triggered by something the man said."The male, after saying something, has obviously upset this group and has been punched and kicked unconscious," Detective Senior Constable Matt Folvig told reporters. "Then, while his girlfriend has tried to protect him, she's also been assaulted several times." The victims don't know the identity of their attackers, and police have released footage of the violence in the hope the public can help. Det Sen Const Folvig said although they were all drinking together before the incident, the victims were only acquaintances with their attackers. It appears to us that they've just known each other from other meetings at the karaoke bar, when they've been there in the past," he said.The male victim has little memory of the incident, which left him and his girlfriend with bruising. "I'm very surprised there aren't more serious injuries given the viciousness of the assault," Det Sen Const Folvig said.