This is going to be long. But I need some serious help and opinions.

Ok, so my boyfriend and I live together. He works and I take care of his 78 year old mother with Parkinson's disease. She lives with us, obviously. We have 4 dogs in the house. But the one is HORRIBLE. I mean, the meanest dog I have ever met. Like 5% of the time, he's ok. It's bad enough to the point that literally none of his mother's other 4 children come to the house because this dog is mean to everyone that doesnt live here. If someone comes over, we have to trick him into locking him in a room before they even pull into the driveway. Or else there's no getting him out of the window or away from the door because he's in attack mode. This dog can be fine with me sometimes. And I mean sometimes. Usually if I go out to get the mail, I have to trick him into coming with me, or else he won't let me back inside the house. I'll have to sneak in through the back door and hope he doesn't see me.

Now, to the story that leads to this question. Today, my boyfriend's mother calls for me for help. I walk out of the bedroom and she's laying on the kitchen floor. I go over to try to help her up,and thedog charged me, baring teeth, just being NASTY. Then he'd go over to her and do the same thing to her!!! Growing at this poor old woman! I try to come closer, because, CLEARLY, I needed to get her up off the floor. The dog isn't having it. So I freeze in place and at this point, I'm trying so hard to hold my tears in because he had me cornered. I'm not making a sound or even moving, other than shaking because I don't know anyone that wouldn't be. What happens next? That's right. He jumped on me. When he finally went away, I had to tell her to hold on a minute so I can grab my phone and call my boyfriend. I go in the bedroom and close the door so he doesnt come after me again. Now I'm shaking and bawling my eyes out on the phone with my boyfriend, feeling terrible because I can't help his poor mother up. I go to open the door to check on her and she was pulling herself back up to the counter. But the dog charges me again while I'm on the phone with my boyfriend. He's the only one who can control this dog, so he tells me to put him on speaker. Well, none of the worked because the dog was still acting stupid. We finally tricked him into going into the laundry room with the back door open and locked him outside. My boyfriend's mother was so frightened, she peed herself. Would it be wrong for me to tell my boyfriend that either he does something else with this dog, or I go? I don't want to just walk away from helping his mother, but I also can't be getting attacked and possibly killed for helping her either. The dog is a 3 year old blue healer mix. Not sure what else he is. He's had him since he was a puppy. And he's always been this way. He's not abused either. Just fricken mean as hell. I do not and will not ever trust this dog.