He considered this an auspicious sign .
He entered the valley to choose a site for the construction of a monastery , whereupon he heard three peals of thunder -- a sound produced by the druk ( dragon ) according to popular Bhutanese belief .
Considering this an auspicious sign , he entered the valley to choose a site for the construction of a monastery , whereupon he heard three peals of thunder -- a sound produced by the druk ( dragon ) according to popular Bhutanese belief .