I'm guessing the dude you found was an elite, and just like elites in WoW or SWTOR or W/E they have shit ton of HP.
The reward is that they always drop some loot, mostly blue stuff.
Also this is the 'future'! He might be wearing bulletsponge armour on his tits, so go for the head. Even elites take a bunch of damage in the brains.
Has anyone tried the new Tomb Raider btw? Looks freaking awesome but haven't heard anything about the gameplay.
Oh oh! Hype about X-COM2 hyyyyyyyype!