Did you look at all of the pictures? Why did they have to cut open the top of his head?
Most likely they 'topped' him to make sure everything was OK inside - the article DOES mention that the blade missed an artery by 2mm...
That's my question also. The kid should have instinctively just pulled the thing out.
And if the leader with an open knife in his hand needed to catch someone, he would instinctively simply drop the knife, not throw the thing so hard it penetrates a skull 15 feet away.
I think Darwin must have skipped by this town.