ADHD spouse didn't react to our dog attacking our niece...

Let me start off by saying that my niece is OKAY, our dog didn't actually bite her, he jumped on her and scratched her. He is now at a training facility for a couple of weeks and my niece is learning how to interact with dogs safely. we're glad nothing worse happened...

 so this weekend my husband and I headed to my parent's place for a family BBQ with our 1 year old German shepherd. My niece is 5, and has a hard time respecting dog's space. She's only 5, so that's totally understandable. The first time he reacted negatively towards her about 6 months ago, it was a big deal and I took it as a sign that our dog needed better training. The last few times he's seen her, they've been okay. He actually let her take his ball out of his mouth and has never been aggressive towards any humans. I think this is where we all made a mistake. I saw they were playing together with a stick and my husband was standing there but he was starting to turn around and walk back to the patio. I grabbed my shoes and was in the process of putting them on to go over there with them, when I see my dog on top of my niece, barking at her and she's screaming. I start yelling at my husband to go get the dog and he doesnt move. I yelled at him 2 or 3 times while I'm trying to get my foot untangled from my shoes before everyone else starts running over there to separate them. Finally I get the shoe off and run over there and my husband is STILL JUST STANDING THERE. He hadn't moved! He was just standing there watching as our dog was being kicked off of her and she was moved away. I grabbed the dog and walked him over to my husband who is still just looking at me, and tell him to take him to the car. I hand him our dog's collar, and he just lets go of it and calls the dog to follow him. I yell at him to hold onto his collar so he doesn't run back over there, so my husband grabbed his collar and took him to the car. He didn't come back to the yard to see if she was okay, or to apologize that our dog had just attacked her. He didn't even seem phased that it had happened.

i just don't understand WHY. Why did he not move? Why did he not react? This concerns me for when we have kids, is he just going to stand by idly if our kid is drowning? I just don't get it. The only solution I can come up with is that this has to be a symptom of his ADHD. I have ADHD as well but I make sure to always take my adderal on time as scheduled whereas many times on the weekends, he does not. 

Does anyone else have any experiences like this???