I've kept wolf hybrids for years. As they age the dynamics change and sometimes for reasons I was not privy to.
THEY know though and are wired to respond to certain stimuli that we just don't pick up.
I SERIOUSLY doubt that there is anyone at fault here. I really think it was a pecking order check or confirmation or test.
Don't beat yourself up over it, that won't change anything. Love your dogs and family and do what's right for your situation.
As far as your son goes, explain to him, or this is what I would do, that dogs speak a language that we don't always understand and something went on between those two that your wife missed. It's not that they had bad feelings for eachother or no longer loved his mom, they just had to do dog stuff that is not always understandable to us.
Be the alpha yourself, not being sarcastic, and do what you have to for your pack.