I could be mistaken, but I do not believe Laquisha Booker is the ex-girlfriend. It was the ex who called 911 and has the restraining order on him. She said that he took his keys and refused to give them back. This is inferred from the dispatch call and snope's usage of ex-girlfriend, not fiance.
Three of Blake's children were in the car, two of hers? Blake has six children, this seems like a bad math problem but, sure, whatever doesn't matter who's kid they were, all need to be protected from a violent knife wielding man (if that's the case....)
https://www.youtube.com/watch?v=vr-UWPUiFIk