Hey,
I’m very very sorry for your losing of such a beautiful animal. From the looks and the information you’ve given us, as well as how healthy he looked despite the loose blood in his eye, he most likely attempted to jump out. I have only ever had Black aros, but a friend of mine had two +2 footer silvers, and I’d seen them attempt to jump out right before my eyes. They can also spooke easily if there is sudden movement. From the looks of your tank, I see nothing but ample room, so maybe there was another tank mate or one of the aros went after it. Once again, i have the least amount of aro experience here probably, but i hope this aids you in this process.
mike