How can we send a printscreen as report to Riot?

I've had a troll that intentional fed as Caitlyn because I refused to give him midlane after he threatened to int. He even tried to get the other team to report me for "instant locking" my champion. Gladly the other players remembered that I was the last pick, therefore, I couldn't do such thing.

I'm tired of having this kind of players intentionally feeding on my ranked games because they don't get their preferred lanes or just simply because they are plain awful members of the community who want to ruin the experience.

I've had enough and I want to report directly to Riot instead of that joke system at the end of the game that simple does not work.

I have a printscreen and Riot staff can simply check champion select chat and the game chat (so I don't get accused of altering the image).

Best regards, a pissed off member of the community.