My grandmother's fish committed suicide like that..It was a huge Oscar (cichlid also) and he jumped out of the tank. It had a lid on it and everything but the next morning she came in the living room where his aquarium was and he wasn't in there. He had flip-flopped all the way to the other side of the room. Poor fishy.
When my fish are fighting they hit the lid, but they are not big enough to lift the lid. They're also cichlids. Put something heavy on it that he can't lift so that he can't jump out.