I am not sure what the figure was, maybe an optical illusion but doubt the credibility of the story. Seems like some paranormal illusionary event, but if only 1 of 5 camera's recorded it, it's highly suspect it was the ghost of the grandfather, but I also understand it was a disturbing and frigthening experience! Even when we don't believe in such things as ghosts, tarot, etc, when something like that happens it throws doubt on whether there is some truth in it or not.