Why does Holmes suppose that Sir Charles ran down the Avenue?

Holmes believed he ran in fear, that he'd lost his wits in fright and ran the wrong way.

‘I am presuming that the cause of his fears came to him across the moor. If that were so, and it seems most probable, only a man who had lost his wits would have run from the house instead of towards it. If the gipsy’s evidence may be taken as true, he ran with cries for help in the direction where help was least likely to be."