Question about my 10yr old male blue front amazon?

My 10 year old male Blue Front Amazon (Rio) has been more and more unfriendly in the last year. I have had him since he was 10mos old. He does come out on my command although he squawks. Today he has flashing eyes fanning out tail talking and mumbling. He does that periodically and I leave him alone. Tonight when he came out he was not displaying that behavior in the bird room but he flew on Bia's cage (my Rose Breasted Cockatoo)who is very sweet and friendly and started to attack him!! Full fledged attack!! They have been out together in the same room since Rio was a baby. Bia screamed and I got bitten getting Rio after Bia. Rio then flew wildly around landing on my back a couple of times which he has NEVER done before and going after me! Then before I could sweep Bia back into his cage Rio was back at him. I finally got him on his own cage and literally forced him in with a thick perch. Both birds are ok although poor Bia is traumatized. I am speechless!! I spoke with my bird guy specialist several months ago about Rio's unfriendly nasty behavior and he told me that Rio might benefit from a one bird home with a single person. A gal did come to see him but he was of course not at all interested in even looking at her. So now I don't feel I can place him with anyone! I am thinking of having him euthanized. I am not kidding. I can't keep him here and know my other birds are safe and I can't place him knowing what he can do. I am desperate to hear any feedback before I make the next move. I will call my bird guy too but his shop is closed now and won't open til Tuesday.Thanks Lisa