Min Pin Poodle Mix My Mastiff Killed My Min Pin And I Don't Know What To Do, I Think It Was An Accident But I Cant Be Sure...?

My Mastiff killed my Min Pin and I don't know what to do, I think it was an accident but I cant be sure...? - min pin poodle mix

I had my pug 4 years and thought it was the sweetest dog. I have 2 children under 2 years and it is absolutely wonderful with them ... When strangers come into the house, he barks, but when we run him in his cage and hangs up to leave you. We have a min pin / Poodle mix a year ago, and have typical sibling disputes that thought ended with 2 min pin bleeding, but nothing life threatening, because the difference) in size (140 pounds versus 15 pounds, I the Mastiff just a little "forgotten" that was bigger ... They usually get along very well, they eat together, sleep together without any problems. Last night we were awakened by neighbors who heard the dogs, but it was too late, my dog died ... I do not know what to do, is not induced, there was no blood on barley, and his neck was broken .... But then I continue to trust him with my children? As I said, have never shown any aggression towards people, she has only to other dogs barking, other than the 2 incidents with his "sister"Please help me, I do not know what to do ...