The man and his wife were hiking with both their sons, when the five-year-old slipped.
The father tried to grab him but then fell himself, together with the younger son who he was carrying on his back.
He and the youngest boy suffered fatal injuries and were killed instantly. The five year old was flown to hospital in Vienna with serious injuries. The mother, who saw it all happen, is in a state of shock.
A helicopter rescue team was sent to the scene. The mountain rescue team said that the accident happened as the family made their descent from the Hubertushaus hut.