I hope I did the right thing

BIL and his pregnant ex-girlfriend are at odds with each other yet again. Over the past few months, he has threatened to kill her and various members of her family at least half a dozen times. Once, he even told me on the phone that he was gonna kill her and her mom. I shared this with Brandi as a warning to her. He is not sane and is definitely a loose cannon.
So this weekend, he threatened Brandi (said he was gonna beat her butt and kill her) and said that he wanted to beat Tyler's (their 4 year old son) @ss (BIL's words). He told the GF that he was going to come sit in her driveway until she let him see Tyler (he has no legal rights and won't get them established thru the courts b/c he doesn't want to pay child support--YES, he TOLD me this himself ) He told her he was gonna teach her a lesson in life, etc, etc. So now she is staying someplace in secret where he cannot find her and has taken a few days off of work to lay low. He has guns, even though he is a convicted felon and it is illegal for him to have them. She decided to get a temp protective order, and I encouraged her to do it. Y'all he has pulled a gun on her before and the police were called to his house the night she finally left him. He is dangerous.
I told her to tell the judge about the guns and his felonies when she went to him today for the TPO. She took copies of my emails w/her--the one where I told her he had said to me that he was going to "put a bullet in Brandi's head and in her mom's head." And I think also the one about he felonies.
I love my MIL dearly and we are very close, but now I am afraid she will HATE me forever for telling this, but I felt I had to. If it were just the GF he was threatening, it wouldn't be so bad, but they have a baby on the way and a SON. She is the mother of his children. I could never live with myself if he hurt her or those kids.
Did I do the wrong thing? Oh, gosh, I hope not. I am really worried.

If the cops search his house and find the guns, he will AUTOMATICALLY go to prison for FIVE years. No IFS, ANDS, or BUTS. It's mandatory in GA.

Dawn, well honestly, I think he is truly crazy. People say this in a joking way so often, but I am not joking. Today I looked on line and according to the guidelines in the DSM IV (which is the manual psychiatrists use to diagnose their patients), BIL has the classic qualities of Anti-social personality disorder when it manifests (or grows) into Sociopathic/Psychopathic personality disorder. From my research, it seems that people with Anti-social personality disorder outgrow their symptoms and behaviors by the time they reach their 30's, but if they do not, then the ASD becomes Sociopathic/Psychopathic PD. If you look at this list: (The ones I underlined apply directly and without question to him and only THREE have to be present to be diagnosed)
List of Common Sociopathic Traits
pathological lying,conning/manipulative, lack of remorse or guilt, shallow emotional response, callous/lack of empathy, parasitic lifestyle Egocentricity; Callousness; Impulsivity; Conscience defect; Exaggerated sexuality; Excessive boasting; Risk taking; Inability to resist temptation; Antagonistic, deprecating attitude toward the opposite sex; Lack of interest in bonding with a mate irresponsibility, failure to accept responsibility for their own actions,many short term relationships


He is a sick person. I honestly believe that given certain circumstances, he would snap and do something very drastic.
BIL tells his side of things with a lot of changes (LIES) and exclusions. I have experienced this first hand when he and I have argued and then he retells what happened and it hardly resembles reality. He lies to make himself look better, to make others look worse, he just lies a lot. The thing is that MIL knows that BIL cannot be trusted and that he is frequently dishonest, but she keeps hoping he will "straighten out." For a long time, she blamed it on the people around him, then on his drinking and drug problems, and now she just shakes her head and hopes he will "get better and do right." I think she sees what little good there is in him and hangs on to it. Personally, I see no good in him, and it's a terrible thing to say, but just the truth. As you all know, he is a complete TAKER and never gives of himself at all. I could go on and on, but believe me, he has the above outlined disorder. Also look up borderline personality and narcissistic personality disorders. Those, too are him. But as for MIL, I have told her a lot of what the gf has shared with me, but BIL tells MIL that the ex GF is "white trash" (I always ask, "Why was he with her then?") or that she was only using him (What for? He has NOTHING!) or that she was abusive to him, etc, and so MIL gets caught up in it and is not sure if there is truth in the tales he spins or not. (I say NOT, but MIL knows I am not a fan of BIL, so I have little influence with her in regard to him.) Anyway, it's so complicated. Deep down MIL knows how he is, but I guess the bottom line is that she is his Mom and loves him and tries to protect him even though he brings it on himself, you know?

I am terrified at this point because IF he finds out that I have been communicating with Brandi and encouraged her to get the PTO, much less gave her info, he will be so livid, and who knows what he will do. We have an alarm on our house, and even though we live in a subdivision with lots of people, etc, when I am here alone, it is ON, ALWAYS. I would never answer the door for him if DH were not here. We also LEGALLY own two handguns, and I know how to use them. (In fact one of them I owned when I was single and living alone.)
He has gone to drug rehab a couple of times and spent a long time (YEARS) in therapy, but I don't know if the therapist ever diagnosed the disorders. BIL would never admit it if the doctor did diagnose something so serious. From all the research I did, there is no real effective treatment for the disorders, not even drugs. Isn't that SCARY as H*LL?
BIL really hates me and always has, and I think if he did anything to this part of the family it would be just to me, not to Kyle or his mom. I do think he would take Brandi and her whole family out. This is what he told me about killing her, "I want to put a bullet in her (Brandi's) head and her mom's, too. I mean, I know she is carrying my child and all, but she hasn't been born yet, and that is just how much I hate Brandi."
I am very careful and will not expose myself or my daughter to him in a situation that could turn bad or anything like that. I know better. Many years ago I ran into him at the grocery store and he showed his @ss right there, and I saw the writing on the wall then and since that evening I have been very cautious in dealing with him and will continue to be.

Thanks for your support ladies. It was hard to do, but I am driven by what is right to do, and I really felt it was the right thing. I am also loyal, so doing this makes me feel slightly disloyal to MIL, but in this case (as in most cases) doing right was more important than loyalty.
Thanks again for the much needed support. I really and appreciate you all.