BIL threatened to kill our unborn baby

My husband's brother took care of him because they were taken into CPS custody when my husband was 2 and his brother was 5. His brother was taking care of him because their foster parents were super abusive. His brother took care of him his entire life and I'm sure his brother was lovely when they were younger. My husband always tells me how his brother would take care of him but his brother has mentally lost his way. My husband told me his brother would take being beat and being raped to keep it from happening to my husband and as they got older he started to lose his mind and resent my husband and when my husband was in his teens his brother completely mentally broke after he suffered one of his most violent rapes by multiple men and my husband was forced to watch so his brother kind of turned on my husband and when he got mad would physical abuse my husband. My husband has spent time making excuse after excuse for him saying he never would have done this when they were younger but his brother is insane now.

My husband has tried to help his brother but mentally I think he's long gone. I'm pregnant with our first baby and we had a Christmas party and my husband invited his brother to be nice. His brother got mad and started yelling at my husband about how he had this big house and wife and baby and he has nothing. My husband tried to calm him down but his brother punched him and was on top of him hitting him. I tried to make him stop and his brother said "Touch me bitch and I'll smash your unborn baby through your stomach." My brother had to get him off my husband and kick him out. My husband closed the door and locked it while his brother was screaming outside and I tried to call the police but my husband stopped me.

This isn't the first time my brother in law has hit my husband in front of me. My husband refuses to call the police on his brother and he just says "He's been through a lot." "He's not the same person." "He took care of me as a child." Like he just threatened to kill our baby! My husband has agreed to distance himself for a while and when he does see his brother he will see him alone. How could he want to be anywhere near this person! His brother is a violent crazy person who needs to be behind bars.