Tonight I opened Rita up in the hopes of finding an answer to this strange death.
I think I've found it. It appears she may have had a ruptured aorta.
When I first looked at her heart it looked normal but behind the heart there was a large area(3 inches long) of pooled blood.
When I lifted her heart out of a closer look I noticed the backside of it was the same color as the clotted blood.
The second photo shows the unclotted blood that was in the lower part of her body.
Tomorrow I will take her to my Vet. for his opinion.