The strongest I have ever felt this - high level spirit energy and activity - is around dying children. Children seem to be a lot more aware of their spirituality than adults give them credit for. We, adults, seem to lose so much of this awareness - of our spiritual and divine nature - as we grow older.
I have been in the presence of many dying children. The only way I can describe this is that, at these special times, I have been in a holy presence - far beyond my poor understanding of reality. Children gain a special kind of wisdom and a high level of spiritual understanding - and they have no fear of death.
I have never had the opportunity to observe the aura of someone dying, shortly after an accident, so cannot comment on this aspect of death.
Premature Death
I have, though, known healthy, vital people, that have died suddenly, from strokes, heart attacks and brain aneurisms. I have observed them, in the days and weeks prior to their premature deaths. I have noted similar changes, as I might expect to see in a dying person: very milky-pale-blue expanded auras, silver and white sparks, and lots of spirit energy and activity around them. These people, though, were not sick. They were all, healthy, vital people, but there was something quite different about them - an indefinable atmosphere. In all cases, they seemed to know, intuitively (but not consciously) that their time in this world was nearly up. They all did certain things, tidied up their affairs, or made things right in some way, in the days and weeks prior to their death.