why horses kill their own

Question
My cousins horses are all geldings and have been together for around 4yrs in the same pasture. I happen to witness the 4yr old and 12 yr old beating up the 20yr old. One would grab his neck while the other kick him. BY time I ran to get my cousin to help they had fracture the shoulder of the horse and he had to be put down.It was the worse thing I have seen. The horse they killed was a wonderful horse.I have horses of my own for many years and have never seen this kind of aggression. What would cause this?

Answer
Cheryl,
I will confess that I am not sure about the answer to this.....I am doing some research into the question to give you a better reply. One person I asked expressed disbelief about the whole  incident, but at a barn where I teach the same type of thing happened though I did not witness it.

There was an aged horse in the pasture-they had been turned out for a while together, and suddenly one of the younger geldings attacked  this horse so brutally that the horse had to be euthanized.

The only answer that the owners cam up with sounds implausible to me, but it was that horses can sense when a horse is nearing its own death, by age or a condiiton that we may not even yet know about. For some reason this results in them attacking the old or ill horse. This certianly sounds _unhorselike", but these guys definitely had enough apace and room, etc.

I will contimue to research this, and if you fidn out anything, please email me ay Summersdressage@aol.com.

Thank you.

Mitzi summers