ex best friend

ok so my best friend of 9 years was married for almost six years. she has two children with this man the kids are 5 and 2. they got divorced about 3 months ago and my best friend started dating this new guy named Jeff. they moved so fast. within a week he was moved into her house and playing daddy to her children. he would spank the kids all the time and brag about how he had to whoop their asses to my husband and I. he also kicked her dog in the face repeatedly right in front of us because he was barking. my friend has always been strong willed and I couldn't believe she was letting him treat her kids and dog like that. I found out that he was on strong pain pills (not prescribed) and got her doing them also. they were spending over 1,000 dollars a week on them. she kept letting her ex have the kids when it wasnt even his time, just so she could spend more time with Jeff. She would call me to babysit and I always would. one day Jeff came to get them and they were crying and clinging to me begging me to not go with him. the 5 year old told me he hits them (which I had seen plenty times with my own eyes) and that they were scared of him. i told him it needs to stop and even though I didn't want to, I let him take them. My best friend called me and was mad and told me to mind my own business. I told her that I hate Jeff and as long as she is with him I want nothing to do with her. he is abusive to the children and I couldn't believe she was doing and putting up with all of this. so after that fight I have not talked to her for a month. her ex husband called me saturday and told me he is worried because the kids are scared to go to their moms and asked me if I knew anything. I ended up telling him everything I knew. I felt bad and somewhat regretted telling him but if I dont help these kids and something happened to them I would never forgive myself. her ex husband went to childrens services today and is going to also try to get custody. after researching we found out that jeff just did two years in prison and is on parole. so her ex also contacted his parole officer about the drugs. i am upset that now i am in the middle of this and now a witness and have to speak to childrens services on his behalf. they say it will be anonymous so I pray it is. I know she will hate me forever if she finds out. i just want my best friend back. and i want her kids to be away from this abuser. do you guys think i did the right thing? or am I out of line?