its recognizable, there are his tattoos, and the conversation before that between the bridge and the hangar gives u an answer if u wouldnt know who is the mutant, remember? "Hangar crew, this is the bridge! Fifield monitor is just popped in...."
and yes, i belive Janek and Chance kill him in both version, only changes that Shaw, Weyland and his bodyguards enter the hangar during the fight, maybe they run to the apc , one of them gets killed by the axe and Shaw drives over Fifield, then the pilots kill him.....and what would build up to Janek's sacrafice is the extended scene with the x-mas tree, where he says first "im just flight the ship"...thats why Shaw mention that in her room to Janek in the end