He's never been aggressive to people before, let alone DD. I left them alone for two minute when I went to answer the door, I come back and DD is hysterical as she has been bitten on her arm. I don't think the dog meant it as no skin has been broken and he's a Rottweiler so if he really wanted to hurt her he could have. But like I say he is normally so good with him, I didn't think twice about leaving them for afew seconds. DD is 6, dog is 10., could it be dementia? Not sure where to go from here.