As far as we know about Shaun, he's a psychotic scientist/engineer who makes chemical weapons for god knows what reason. We also know he's a true weasel at heart as he's always lurking in the shadows. You best hope he doesn't get the drop on you because he most certainly knows how to use that toxic flamethrower properly. Everyone thinks he's weird since he never takes his suit off, but the truth is he's planted toxic radiators all over and is slowly killing everyone over time while they're blissfully unaware. Again we have no idea why he does this, but he's clearly got big plans...