Engineer dying?

When the hologram of the engineers running down the passageway appeared. The last engineer, tripped and was decapitated by the door. It was assumed he was either attacked or was being destroyed by the inflection of the black goo.Personally i believe the later, i also believe the infection is the reason for the pile of dead engineers. Since the the engineer was decapitated, the effects or progress of the black goo may of stopped. And when shaw and the doctor injected the engineer's head with the probe, the progress of the black goo restarted and its head exploded ( just like the pile of dead engineers). The black goo has been described as a substance to accelerate evolution, sometimes with bad side effects particularly humans (fifield). Maybe the engineer in cryo sleep was infected with the black goo and because he was in hyper sleep the progress of infection had stopped (maybe he knew he was infected and put himself in cryo sleep with the hope he might get saved) With the infected engineer being impregnated by the tribite, the results were different eg the large deacon. It was because of the black goo which was in the engineers body, thats the reason why the deacon was so big ( a double effect).If the engineer was not infected, the results would have been different again eg normal sized xeno.