i'm sorry to hear of your situation, sounds like the boys have a periodic go at it to establish or re-establish who is the alpha dog of the house. Male dogs may be best friends one day and fighting the next but it is extremely rare that one will kill the other. Generally they only want the other dog to submit to them and will stop when that happens. i agree the wounds can look horrible and it looks like they were trying to kill each other but that's probably not the case.