That's not teeth. That's their gums being exposed and pulled tight.
Madness string 83064
Your job is to mourn your friend. He is gone and there is a hole in your life where he used to be and that's got to hurt like hell.
Kids sometimes latch on to the oddest aspects of a situation. They're people with opinions and experiences and priorities, and their emotions are close to the surface, and no amount of reasoning with them will always get the outcome you think is correct.