The "red ooze' was most likely blood releasing from the capillaries located in the rays intestinal tract. Once death and decay set in capillaries begin to degrade first. By degrade I mean burst. The intestinal tract of every animal is rank with bacteria (helps us digest) and this very bacteria is what sets in motion the decay process.
The anal sphincter, a muscle, loses tone (control) at/after death and as a result acts like an "open door" for the decay process. The capillaries in the intestinal lining breaking down and bacterial action tend to leave easily out this "open door".
With us humans it is no different.
Condolences,
FireMedic