The walkers were traveling along the popular Bridal Path when the bizarre incident happened on Sunday last.
The bird, one which was reintroduced to Ireland as part of a breeding programme, crashed through trees and landed on a large boulder beside the group.
The bird, known as Fiadhna, had the letter F on its back as well as a satellite antenna when it fell close to an area known as the Long Hollow.
Rangers knew the bird was in the area but its solar antenna had ceased working and it had been thought she had been killed.
The walkers from Derry managed to snatch a picture of the bird before running for help more than a mile away at Glenveagh Castle.
Pat Vaughan of the National Parks and Wildlife Trust rushed to the scene and despite getting there just half an hour after the crash-landing, Fiadhna was gone.
A group of rangers carried out a full search of scrubland around the area but there was no sign of the majestic bird which has been tracked to many counties including Kilkenny, Clare, Galway, Louth, Kerry and Tipperary.
Lorcan O’Toole of the Golden Eagle Trust said he thinks a pair of Golden Eagles which are living in the area may have attacked Fiadhna.
“The only reasonable guess we have is that the White-tailed Eagle was simply dive bombed by a territorial Golden Eagle and struck in mid air, by closed talons and fell to the ground as a result.
“This may account for the commotion heard overhead, but not seen, before the eagle crashed through the treetops,” he said.
Mr O’Toole said it was encouraging that the ancient competition between White-tailed Eagles and Golden Eagles is once again playing itself out above the Mountains and Loughs of Ireland.