Dogs killing livestock

Question
New Years Eve I let my dogs out to run (I have four large breed dogs of malamute/wolf and husky/wolf types), I was notified by a law enforcement that they killed 3 sheep.  Today when taking them out to the pen, the leash of one slipped and 3 of them ran off. 2 hours later after driving around looking for them, they came back with blood all over their faces.  What can I do to stop them from killing other animals if they get loose?  They are very strong dogs (sled types) and when I or my 11 year son takes them to the pen they, at times, are so strong they pull us down and get away.  Our intent was to breed a sled-dog team for fun for me and my son. I knew they are a powerful breed when I got the 2 new malamute/wolves, but all 4 together has become overwhelming.  We have an 8 year old male husky/wolf, a 8-10 year old female husky/mutt, and 2 (brother & sister) 9 month old malamute/wolf mix puppies (they are actually bigger than the adults now).

Answer
I presume these dogs are wolf hybrids?  The lower the hybridization, the more dangerous these dogs are.  The higher the hybridization, the more unpredictable they are, because they are not dogs, and they are not wolves.  These dogs need to be maintained in a large pen with very high, double chain link fencing (gate to interior fence, gate to pen.)  They cannot be allowed to escape; they are hunting in a pack, this is natural behavior.  You cannot extinguish it.  In many states it is against the law to have a wolf hybrid of any percentage.  Owning dogs such as this often requires a license; and it always requires extreme expertise and careful management.  DO NOT ALLOW YOUR CHILD TO HANDLE THESE DOGS.  The possibility of one (or all) treating him as a subdominant member of their pack and turning on him IS HIGH.  Look for a wolf sanctuary as close to your geographical area as possible and make EVERY EFFORT  to place these dogs in appropriate hands.  YOU ARE NOT capable of managing them.  They are potentially quite dangerous to humans.