BBM.
I had that thought briefly as well. What if it was an accidental death? What if she was having an affair or hired someone to drive with her in the trunk and fake an abduction but she died from fumes or the suffocating heat of the trunk. Then the accomplice paniced, shot her in the chest and closed the trunk to make it look like suicide. This came into my mind when watching Nancy Grace's expert talk about why they would wait for toxicology reports before determining manner of death. I think this is highly unlikely, BTW, but it seemed just as likely as a hit man or a suicide at the very beginning when we had very little info. As things trickle out, it does seem they think she made up the abduction. It remains to be seen what the cameras and forensics will reveal.