At what age do they suddenly become treacherous?

So today, I took my nephew, The Spud, out to play lazer tag along with Aaron of The Shekel and his daughters. Now up until this point, my newphew has always been loyal and dependable and I could count on him to watch my back. But this time, for the first time ever, the little rat bastard turned on me and began shooting me every chance he got, to the point of just following me around and shooting me pretty much exclusively. And when the final scores came out, he was in his glory when he saw how many times that he shot me, his uncle and mentor.

At what age does adoration give way to betrayal and treachery? Why does this happen? 

I'd ask him, but he's still walking home from the game arena. I hope he gets here before the rain starts.

Aside from that issue, it was a great time. The place didn't have many people there today so every game we played, it was Aaron, his kids, me and the Spud vs. anyone and everyone else who showed up. And we kicked some serious ass, even when outnumbered better than two to one by a whole extended African-American family during one round. That was a good game, starting off with us surrounded by them and Aaron humming "Men of Harlech"as the game began. (Of course he'll say that it was me, but I'm sticking by my version of this that pegs him as the guilty party.)

Good times, good friends, and a formerly good nephew...some days are hard to improve on.