Snake Vs. Snake: Rattlesnake Responsible? What Killed This Bull Snake?

This deceased Bull snake (Gopher snake) was on the road but without any apparent vehicle trauma and coiled in on itself, mostly upside-down. (See "Snakes & Snapper"). Also odd was its "inflated" appearance which I took to be a recent meal until later brain cell processing/review shows the entire body was swelled up/puffy from head to tail. ... waitaminute ... perhaps there's something to see after all?