In my area, any "unattended, unexpected" death is treated as suspicious until proven otherwise.
For example, if a 37 year old woman is found lying dead in the floor of her home with no obvious cause of death, it is treated as a suspicious death. Then if the autopsy finds that she died of a massive brain hemorrhage resulting from the rupture of a malformed blood vessel probably present since birth, the "case" is closed. On the other hand, if she is found to have died from a massive brain hemorrhage caused by blunt force trauma to the head, then evidence has been preserved and law enforcement has the beginnings of a case. There is no "Ooops, sorry, we messed up," no apologies to the family and the community.
It strikes me as an eminently sensible way of handling these unfortunate events. Better to have ten "suspicious deaths" that turn out to be natural causes than one case in which a murderer goes free due to law enforcement's wrong assumptions.
In this woman's case, sure it is entirely possible that she could have died from something like that unexpected unsuspected blood vessel issue. It surely stretches credulity that her vehicle would then catch fire with her in it, just at that precise moment. Then to say that her headlights ignited her antifreeze, well, please! What did she have in there, rubbing alcohol? The only antifreeze deaths I have ever heard of were from ingestion, not ignition.
DC has the exact opposite position regarding suspicious deaths than your community does. They desperately try to downgrade as many potential murders as possible, because year after year their murder rate is one of the highest in the nation. Politicians run campaigns on the lowering of this stat - so many ‘indeterminate’ deaths do not make it to the murder stat column.