They're not talking about it because he wasn't killed, Harry. I thought the Matron might have told you but I suppose she's been busy herself. He died of a brain seizure- a stroke. And after checking his wand we learned that he was the one who obliviated Viktor Krum, too. I'm sure it sounds strange to you, but people can do funny things when they have a stroke. That's how my own Father went, and he could barely speak, his words were all wrong. It's like a violent storm in the mind that sweeps through and rearranges everything...

It's still a bit mysterious why he came to the castle- if he was just addle-headed or if he was after something in particular... so if anyone starts asking you questions about it, be sure to let me know.