Complex sentence: Ingrid Loyau-Kennett, a cub scout leader from Cornwall, one of the people at the scene disembarked from a passing bus, with the intention of rendering first aid, when she saw what she thought to be a road accident.
Split into simpler sentences: Ingrid Loyau-Kennett, a cub scout leader from Cornwall, was one of the people at the scene. She disembarked from a passing bus, with the intention of rendering first aid, when she saw what she thought to be a road accident.