herd behavior in my off the track tb

Question
My horse is an 8 year old retired track winner and i have owned and adored retraining him for 2 years.. he is very smart.   My horse, Tanner goes out on turnout with mares and 2geldings , nine horses share a 25 acre pasture for 8 hours everyday.  My stable has many senior horses and one old Arab mare went down and wouldn't get up in the pasture.  She is 28 and has cushings disease and my horse was caught trying to pull her to her feet by her halter and her neck...went so far as to charge the angry horses owner when she came out screaming at him and then the mare got up and Tanner tried to drag her by her halter away back to the herd.   Has my horse gone insane?   He is not the head gelding but is not at all agressive towards any of the herd and gets along well. He didn't hurt the mare and the did not break her skin on her neck but it is swollen and the owner is mad at me ..... and my horse she thinks is crazy.  Please help .

Answer
Hello Wendy,
My I have never heard of such a thing! Here is my take on the situation. Your horse is not crazy, they were having somekind of a conversation in "Horse" and I am sure it made sense to them both. Turning out horses is like turning out several children to go play- it is important to let them learn to interact, and YES, it is important to get involved if it starts getting to tough. Perhaps this horse who is so much older with cushings should be out with just one mellow friend. Its tricky to say having not been there, but if your horse was wanting to be pushing this mare around seems like it would be more natural to kick her while she was down. If you can start a dialog with the owner and ask if perhaps you could take them out together just the two of them- perhaps with some food in two piles for each- and just sit on the side lines and watch you might get a better sense of what is going on. I can understand the owners concern for her old dear friend, however it seems to me-though I cannot know for sure-that your horse was just being a horse and her dear friend might need a little more shelter from the energy of youth.
Good luck in working it all out!
Best Wishes