Could be wrong of course, but my first thought about the person on the floor was that it's the guy wielding the flamethrower in trailer1... But i dunno...
The 'alien-looking creature' with the odd head still has spots on his suit on fire. In trailer1 someone was seen leaping on the flamethrower guy, but that person had clearly defined human facial features - was it the mohawk guy? Thanx for the additional HQ stills of this... thing... Just confirms my first impressions.... (shivers)...