The heart will stop pumping blood and the blood becomes stagnant. The cells will cause it to coagulate making it thick. The muscles stiffen and the blood falls to the bottom of the corpse. Sometimes the dead body will build up gas and bloat up, also getting some blood near the mouth area which creates an appearance similar to that of a vampire that has recently drank blood while pushing the eyes out of their eyesockets and the tongue out as well.
The blood will lose its oxygen and the organic remains will draw fungi, plants, and other decomposers to the corpse.