Spoiler, my opinion about the twist

So people on the board are saying the twist is that it was all a dream. I'd like to argue that it wasn't a dream, it was some sort of purgatory, and the creepy hairless guy is a harbinger of hell. All three were on the precipice of death, and all three were on the verge of going to hell. Our main protagonist fought his way back because he didn't throw the grenade that killed the civilians.

The reason for my theory is: He new Angelina's name, which was odd and unexplained. He saw his fellow captives injuries, which are likely consistent with the injuries they had in the "real world", and how would he know about that if he wasn't able to witness it himself.