In the arches, which were storage places for cargo, down at the shore-line, people gathered to take shelter from the ash. Unfortunately they were engulfed by the superheated pyroclastic cloud and instantly killed.
Their skeletons were preserved in the ash and remain as testament to the power of the volcano.
Looking at the skeletons of these poor people enables one to get a clear picture of what happened in those last hours. It must have been terrifying.