Dog attacking another dog

My good friend had a tragic situation occur the other day and I'm trying to help her make sense of it - if that is even possible. So I will ask here for your thoughts and opinions.

My friend has a 9 year old, 60 pound chocolate lab they raised from a puppy. He has always been calm, well-mannered and sweet around other animals. Their other dog was a 7 year old, 4.5 pound female yorkie they raised from a pup. The two dogs seemed to love each other for years. The lab would groom her and they would sleep together, the lab often being the one to initiate the cuddling.

A week ago, the little yorkie was crossing the sofa to cuddle in with the lab (something they have done with no issue before). Right before she got to him her foot caught in the cushion and she let out a yelp. That's when the lab went for her, grabbed her by neck and shook her violently. My friend who was in the room and witnessed all of this screamed and he dropped her only to pick her back up again (it gets a little graphic here, please be warned) by the head and crushed her skull. Of course she died instantly.

What are your thoughts on why this might have happened? Oh, and they did take the lab to the vet the next day for a complete check-up and full bloodwork and nothing unusual was found. Also, the lab was neutered and the yorkie spayed, both when they were around a year old.

I know it's just an educated guess on your parts as you have no first-hand knowledge of these dogs nor have you seen their interactions, but any thoughts are welcomed.

How tragic.

My suggestion is that it was predatory drift, triggered by the yelp.

If I am correct, you could reassure your friend that the lab hasn't suddenly developed aggressive tendencies; prey behaviour (notwithstanding the awful outcome here) is natural, and while she might need to be careful of the lab around smaller dogs, it is unlikely to affect the dog's behaviour around the family.

So sorry to hear this, my heart goes out to your friend...a devastating thing to happen. My only thought is that maybe the yelp of the yorkie triggered something in the lab, but what or why I wouldn't know... Years ago I lost my old yorkie in a similar way, I had a lab cross too and we used to walk in our local park regularly with a friend who had a yorkie and a collie cross, one day out of the blue, the collie picked my yorkie up by the head and then dropped her, right in front of us...she died in my arms.. there was nothing unusual going on that we could see, it was seemingly unprovoked and random...but it just happened in a blink. A difficult thing to come to terms with when you can't understand why it happened. So sorry...

I'm so sorry this has happened. I've nothing to suggest other than what has been said, but really hope your friend can come to terms with what happened and not feel differently towards her lab.

Thank you all for your thoughts on this, I will pass them along to my friend.

Flobo, I am so sorry for your loss as well.

This is horrible.
And scary.

I am so very sorry. I hope your friend is able to access the right support.

With my Behaviourist hat on, I have to say that this is not unusual. There are often small (to us) signs a long way before this kind of event occurs, but these signs are easily missed. I suspect the Yorkie had an underlying health problem, which can go either way with dogs they share the home with. Sometimes the other dog becomes protective, but more usually (as is common with social animals including us) the other dog becomes more and more uneasy, because in primitive terms, the sick and weak attract predators. This tension builds until a trigger occurs, which in this case was the Yorkie screaming.

This does not mean that the other dog is bad or will attack a child or enjoyed the process or will attack another dog ever, though if mine, I would put that dog on a lead anywhere it might encounter a very small dog or children who are screeching and running about. This last has an outside chance of the dog becoming fired up and redirecting but it is a very slight chance - I'm simply a belt and braces person.The owner was wise to get the dog vet checked, because not infrequently such behaviour can mean the attacking dog has an underlying health problem.

I have attended many many consultations where dogs that have lived together for years in apparent harmony have set about each other. It's dogs. It's what they do. Usually there have been plenty of warnings but you have to be very dog-savvy to see them.

Your poor friend. She must be in bits.

This story gave me a pause, I have to say. We have a tiny yorkie as a neighbor, Miles meets her all the time on walks, they love each other and every time we meet they must say hello, sniff, kiss, etc... Although 95 lbs (43 kg) Miles is on leash during these encounters, he is not restrained.

As @Hemlock said above, when I lost my yorkie the only conclusion I could come to was that it happened because she was elderly and did have health problems, maybe the collie picked up on something...but I have to admit it took me an awful long time to come to terms with. Please do suggest to your friend if she finds she is struggling, to talk to someone. My experience was over 20 years ago and I don't think there was such a thing as a pet bereavement counsellor then, but I know now I really could of done with the support of one...

Thank you all for your input. It is most helpful. I am very intrigued by the idea the yorkie may have had an underlying medical issue that triggered this. I have a cat that gets very upset and defensive when one of my other cats gets sick almost to the point of attacking them, so I can easily see how a dog feeling this same way could be triggered.

And yes, my friend is devastated. That little yorkie was very much loved and losing her so suddenly and violently has been difficult. But to her credit she does understand that dogs at their core are predators and that her lab is not now a vicious monster. He is back to his loving, gentle self (was seconds after the attack actually). This gives her hope that this was a one off. I will suggest to her to be careful with him around other small animals, but they live on a horse farm and he is never off their property except to go to the vets so her only concern is their other animals. However my toddler grandson does go to their home now and then as my daughter is their horse trainer. I think using an abundance of caution I will suggest he stay with me when she goes from now on just to be on the safe side. I am also an err on the side of caution kind of person Hemlock so thank you for pointing out being careful with him being around small children, just in case.

I will pass along all your helpful ideas and thoughts. I know it will help her as she deals with all that has happened.