When he did not turn up for a regular gig a friend and his wife went to the Sunshine Blvd complex and found Mr Williams dead in the lounge.
There was no sign of forced entry.
Police are treating the death as suspicious and had not yet determined a motive for the assault, said Detective Superintendent Hutchinson.
He said inquiries indicated Mr Williams died in the early afternoon of December 23 and appealed for public for information from anyone in the area who may have seen people or vehicles behaving suspiciously.
Friend Jackson Douglas, who lives in Brisbane, said he was "shell-shocked" by the news.
"Please send his family my love and if any of the boys can contact me that would be great," he posted on the band's MySpace page.
Queensland police told APNZ a forensic examination of the unit was taking place and inquiries were continuing today.
Senior Sergeant Bruce Pearce of Gold Coast police said the death was being treated as suspicious, but nobody had been taken into custody."We've just got people helping out with the enquiry and statements are being taken at this time. We certainly appeal for any witnesses," he told goldcoast.com.au.
Police would set up a tent at the site for mourning family members.
A nearby resident who called police said he heard a man yelling "don't go inside" about 2pm, the website reported.
"He was shaking really badly and couldn't really stand properly, I guess he was in shock and just overwhelmed."
A resident of the Mermaid Waters unit block, Beau Windon, said he was shaken by the death and was no longer keen to re-sign his lease, which was up for renewal next week.
Police are continuing to doorknock neighbours as part of the ongoing investigation.
