Mr Florence said the offender - described as being Polynesian, of solid build and wearing a light blue, long sleeved shirt - left on foot walking towards Quay Street.
It is understood he was with at least two other people. He also had a tattoo on his right forearm.
A friend of the 25-year-old alerted emergency services to what happened.
"They weren't actually together when they came out [of McDonald's]."
The man was taken to Auckland City Hospital, where he remains on life support.
His family had been notified, Mr Florence said.
Police had already spoken to several witnesses and were reviewing CCTV footage in their investigation.
Anyone with information on the assault should contact Auckland police on (09) 302 6516. Information can also be reported anonymously through the Crimestoppers line, 0800 555 111.