How To Initiate Divorce When The Spouse Doesn’t Want To?

TL;DR at bottom of the post.

My mom bought a house around 2-3 months ago with a new husband, they got married earlier this year so they could get a house loan together and quickly get out of the rough situation our family was in. The husband had not lived with us at all up until we all moved in together. Our family had known him for over 5 years off and on and thought he was someone to trust, take the work load off my mom and her schedule, and help her take care of me and my brother.

The moment all the paperwork was signed, he flipped personalities and turned into a verbally and psychologically abusive monster that terrorizes us all and has threatened to kill my fiance and has had police called twice. Police won’t do anything even if there is video recording because it was obtained without the two party consent. Told cops the first time that we were all terrified he was going to kill someone when they left. Said anything to get them to do something in the moment and not a single thing happened and we were forced to leave our home for a night, then the next night cops were called again and the verbal threat was made. Still nothing. He has a history of domestic violence and assault and police do not take us seriously. He is truly a psychopath and refuses to accept my mom’s plea for a divorce.

He gave absolutely no money for the down payment on the house while my mom put up 40k and all her savings, and all he really has is his name on the house. He is completely unwilling to get his name off the house, discuss divorce, or leave in any way that doesn’t result in us not keeping the house; it feels absolutely unfair that our family has put up so much for this and he put in nothing so he doesn’t lose anything no matter what happens. Mom has been trying to take this to a lawyer for the past couple weeks to see what options we have, and unless he agrees to it, there’s no getting a divorce, not even initiating one. We all are at a loss as to what we’re supposed to do, he has dug his heels in completely and keeps insisting he can “fix” verbal abuse and threats, and to give him time. I can’t sleep at night out of fear of him suddenly flipping out and possibly hurting or killing someone.

TL;DR: Mom bought our family a house with a new husband with a large down payment from her and none from him, decision was made in somewhat of a rush due to the circumstances that had been going on. Husband turned into a psychopath and has started verbally abusing me, her, and threatening to kill my fiance. Police aren’t doing anything and the legal system has left us at a loss. Desperate for advice, and we want to try and keep this house without him in it.
Location: North Carolina, US.