Hostile Mob AI seems buggy

I was underground equipped with a stone sword (no bow) and I encountered a skeleton. As is my custom, i run away for about 16 blocks from the skeleton so it follows me around a blind corner. Then I get a couple of hits in before it shoots me.

The skeleton never followed me though, so I went and spammed the attack key with my sword until it died.

It didn't shoot me once.

My local game difficulty is Normal.