You people and your zig zag are just silly. Honestly, after the second shot or so he would have been so far away that the chances of hitting him were nil anyway.
https://www.youtube.com/watch?v=XqMPkg1QXEY
He starts running at 2:13 and dies at 3:31. He has run for 78 seconds. Sure he's only 4 in the books, but in the show he's obviously older. The actor is 15, let's call the character 12.
Here is a 12 year old running 400m in 65 seconds. Let's assume Rickon is only 3/4 that speed. He's still covered over 300m before being shot dead. The farthest accurage shot ever with state of the art bow technology against a stationary target is 283.5m (
http://www.guinnessworldrecords.com/world-records/mens-archery-farthest-accurate-distance/), and you folks are worried about zig zagging? With the depicted time and such crude equipment, Rickon would have been far beyond the effective range of any bowman.
So there