I couldn't figure out the controls, got locked into a dialogue that didn't seem to do anything. I would also turn down the motion blur, it was pretty extreme
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I found that once you open the chest, you get an item in your inventory which you open by using "I" right click instakills literally anything if you are behind it, but left click is main attack. I think it was E or click or space bar to talk to the guy, either way you should give it another go, its pretty neat