LB - Judges 9

I read about Gid's son Abimelech. Now, Apparently he wasn't a very good guy and he killed all his seventy brothers with a stone. God put an evil spirit between him and his people and they were mad at each other and Abimelech fought against them or something. Dad, can you help me understand this chapter? It's confusing. But it turned out that a lady had dropped somthing metal on his head and cracked his scull and he told his servant to stab him so that a lady wouldn't of killed him. Weird, huh?