Any place I can report someone outside of post match chat?

Basically, I went into champ select and had this dude thrash the entire team off rip and threaten to troll. Someone was in the previous game with him and he did the same thing. I know I can't shame him on the forums by posting his name but we should at least be able to send his name somewhere to have people look into his previous match histories.

I'm sure if he was that toxic in champ select that he is utterly incapable of keeping his cool during a game.

Let me know if there is someone I can contact to look into this dude. I'm almost certain he has a closet full of decapitated heads.