George (Clyde) Little was killed while walking on a steep section of the track near Mackinnon Pass, the highest point on the Milford Track, about 11.30am last Friday.
Mr Little and his wife Jill were part of a 32-member Rotary tramping group, staying at Department of Conservation huts in Fiordland National Park.
The group included people from around New Zealand and Australia. One of its leaders was Otago Regional Council chairman Stephen Woodhead.
Mr Woodhead said Mr Little was walking towards the back of the group, with his wife and two of the group's other leaders acting as ''tail end Charlies'', to ensure no one was left behind.
''The track is in good condition at that point. We know he was walking single file with his wife behind him.
''He slipped down a sloping rock face and then there was a drop off.
''She saw him pop over and he disappeared quickly. It must have been horrifying for her.''
The drop was estimated to be between 100m and 150m.
Mr Woodhead said it had been raining during the morning but it was beginning to clear.
He did not believe either weather or track quality were factors in the accident.
''We have no idea how it happened. We don't know whether he tripped or whether he had a medical event.
''It's just a complete and utter shock to the group.''
The cause would be determined by the coroner, he said.
Mr Woodhead described the couple as ''reasonably quiet'' but keen trampers.
''They were a nice couple.''
Ultimate Hikes general manager Noel Saxon said people on one of his company's walks encountered the group soon after the accident.
''Our guys came across some packs on the side of the track and they knew there was something going wrong off the track.''
He understood the Rotary group had a locator beacon, which was activated when the accident happened.
Mr Saxon said the man's companions were shocked and distressed after the tragedy.
A rescue helicopter flew Mrs Little and her husband's body to Te Anau. Peter Vollweiler, of Waihola, said he had organised the tours for the past 30 years, and during that time about 17,000 people had walked the track without any fatalities.
''Most of them [trampers] are middle aged. We've been pretty lucky.
''We've only had a few helicopter evacuations from the track.''
He planned to meet the tour leaders today.
