Our staffie attacked our other dog in the home

Hi, wondered if anyone could offer any advice. We have a healthy 18month old male staffie Milo. we have had him since he was 10 weeks old. We have 2 children ( 12yrs and 9yrs), and 3 other dogs ( healthy shih tzus 2 males and 1 female) that we already had when we got our staffie. Over the past months our staffie has seemingly randomly 'gone for' the shih tzus. He has had ' a go' at all of them at different times. This takes place only in the home. These incidents are rare and i have always stopped it straight away. However this week he went for the bitch and had her on her back. Last night our staffie went for one of the shih tzu's and for the first time ever drew blood and it was particularly aggressive. He had the shih tzu by the neck and i had difficulty getting him off. The other dogs do not react when milo gets aggressive. We have a good sized house so the dogs dont live 'on top of each other'. I clearly cannot let the shihs tzu's mix with milo now even when i am with them as these incidents seem so random and i cannot figure out what the trigger of the attacks is. I am worried how practical this arrangement can be. Milo is a beautiful loving dog with the family. Any thoughts would be greatly appreciated. Thanks.

You say he's always done this? But now it seems worse?

Is there definitely no common trigger that you can think of?

Sorry I do not have any personal experience of this as I have only ever had one dog at a time, you may find the link below useful. I would aslo add that staring can be seen as a challenge to a dog so this may well be something else to look out for:

http://staffy-bull-terrier.com/dog_body_language

Hi Caryll, thanks for your reply.  Milo hasn't always done this, it started a couple of months ago.  It has only happened about 5 times. Though this week he went for the bitch shih Tzu and then last night one of the males.  Up until last night the times it have happened,  he has been rough, but more just noise and he has got the other dogs on their back and been on top of them. but i have been able to stop it by shouting at him and pulling him away.  Last night was different though. He was far more aggressive, i managed to get him off the other dog, but it was not easy to do this and the other dog was bleeding on his neck and face.

Hi Kathy, thanks for your reply. Last night when it happened my back was turned, so i didnt see it start.  All the dogs seemed calm at the time though.  It's really strange, they will lie happily together, go out together, even play together, but then something like this will happen.  I think there is a trigger that i am clearly missing and i need to understand their body language more. Thank you for the link i will certainly check it out:

I just wondered, are there any toys or bones on the floor? That could be a trigger, I know Axl will react to any other dog that tries to take his ball or bones!

was your bitch in season or coming into season by any chance?