The accident occurred in the high mountain sector of Grands Montets. Indeed, the three mountaineers went up to the face, then crossed the Col des Rachasses at 3.037 meters above sea level.
According to Le Dauphine, in their route of ski mountaineering when they reached the Argentière glacier, one of the three fell into a crevasse at the level of Gros Rognon at 3.541 m altitude.
The man fall more than 15 meters into the crevasse. Unfortunately, he died on the spot.
Arriving on the scene of the accident, the Chamonix high mountain gendarmerie platoon could only declare the man dead.
Source: @Le Dauphiné Libéré