What do you do with a Bully? -friend murdered

My husband's close friend has a sister who was brutally murdered 2 days ago in her driveway by her neighbor. The neighbor was said to cuss her and others out, harassing many of his neighbors.

His initial plan was to murder their son but when the mom came out of the house to get the mail he decided to kill her instead. He hit her with a baseball bat from behind as she was walking back to the house then stabbed her multiple times. She died in the driveway while her husband and kids were in the house.

Here is where I have difficulty... her brother (my husband's friend) is reactive, went over to the neighbors house a year ago and confronted him, told him to leave his sister alone, welcomed him to fight with him if he has a problem, and threatened to come after him if he hurt his sister.

The husband never confronted the neighbor, took a passive stand.

Each man blames the other.

My initial reaction was exactly like the husband. My husband said I used his exact words - "her brother stirred up the hornets nest" …and put a deeper target on their family.

Her brother blames the husband and the whole neighborhood for not standing up for his sister these past years. The woman who was stabbed talked back to the neighbor for calling her names. She said things like, “it makes you feel like a big man to pick on a woman but when my brother came by you were a coward”... again, stirring the hornets nest.

To me, stirring up the hornets nest seems similar to a mob family. They makes enemies, putting a target on their family with their threats and anger towards others. A quiet meek person (hopefully) fades into the background, not making enemies, and becomes a soft target for verbal abuse and taunts.

To finish the story, my husband's friend who threatened the man, who's sister was murdered, went home to get his gun to kill the murderer's family in front of him but his eldest son was one step ahead of him. He already gathered the guns in his house and took them to a different location until his father cooled down.

My cell phone must have heard me talking about bullies last night because videos popped up in my feed on how to handle a bully. (I have never looked up anything about bullies before!) I watched them. All of them showed bullies keep escalating if they are ignored. It made me question my passive stance.

Does anyone have any thoughts on this?

What would you do if your neighbor was an unhinged bully?

Does anyone have a success story from bullying the bully?