He takes the chopper and splits his own cranium as the Doctor would say.

Obviously he crept up behind swung this chopper and brought it down splitting the cranium.

Now, you can see that this headset was designed... . ..for something much bulkier than my human cranium.

And also we wanted to free up the ears, so the sound actually goes through, conducts straight to the bones in your cranium, which is a little bit freaky at first, but you get used to it.

But the real issue is that we are guided by our limited experience, and until we can think out of the box of our cranium and what we know, then we can't recognize what to look for, or how to plan for it.