I just started my chickens back after 4 years I was sooooo excited. I bought 12 9 week old commits . I had them 1 week and something Killed everyone of them. We had them in a fenced in stall locked and let the free roam during the day and locked them up in the evening. Went to see them one morning with my grandbaby she loves the chickens.. and 7 were gone couldn't find them and 5 were dead with heads gone and it looked like the hearts were gone I cried for two hours.. What could this be? No signs how they got them I just know they did..Someone please help me figure out what to do to make them safer before I buy more.