Sorry to hear of your situation, Jamie. Definitely see about finding a good psychologist; it is human nature for the kids (and likely you) to second guess if it is their fault, or if there is something they could have done differently. They don't need to grow up with that kind of baggage.
I have a brother with similar issues, and if nothing else, I appreciated talking with a shrink to better understand and accept my brother's condition, as well as knowing that his is not an uncommon situation.
Hopefully, there are some good people in Child Protective Services for your area. Tragic though it is, you are lucky that you have the police as witnesses.
You'll be in our thoughts and Godspeed in returning your home to a healthy environment for the kids!
Kurt