Our English Mastiff is about 2 years old now, 210 lbs and is ordinarily a good boy. However, yesterday was the SECOND time that he attacked our male weimi Max!! Max was sitting at the edge of the bed wanting to get up... and Rocky (out mastiff) was standing right behind him. Max kind of growled a little, like a just leave me alone thing, not aggressively or anything, and I smacked his bottom and said Max stop it... and as soon as I finished saying that our mastiff just nailed him. He grabbed him by the neck and shoved him to the floor, started rag dolling him... we were screaming and hitting Rocky with anything we could grab (my husband a hanger he had in his hand and I grabbed a glass perfume bottle. I was kicking him and shoving him trying to get him to go down while my husband was hitting his legs trying to make him fall down as well. Nothing was working! He dragged my Weimi across the bedroom floor where I finally jumped on top of Rocky and knocked him to the ground and held on tight while my husband yanked Max out of his jaws! I'm not ashamed to say that I beat the crap out of Rocky and was screaming at him at the top of my lungs while my husband looked Max over. Luckily he is okay. But this is the SECOND time!! The first time, Rocky was in the bathroom while we were giving Max a shower... and as soon as we opened the door to the shower and Max came out and shook Rocky attacked him. I don't have any clue what could be going on... or why he would feel he has to attack Max!! We have 3 other dogs and he never attacks any of them... just Max (the other three are girls). The one thing we have noticed is whenever we punish a dog by smacking them on the behind he comes running up and barks loud and fast at them and gets all worked up. We are worried about having to let Rocky go to another family which we don't want to do, but if Max is continuously in danger we don't want to come home to a dead dog one day! Does anyone have any idea what may be going on? Or has anyone else had any issues with this?? Any help anyone can give us would be greatly appreciated!