Boosted player ruining games

What is the proper way to go about reporting a player whom is suspected of being boosted? I take this very seriously and have never suspected someone of this in the past, however in this specific match there is not a single doubt in my mind this guy was not the owner of the account he was playing on. His mentality in game was that of a child, harassing teammates the entire game, whilst taking lux toplane, dying several times, then going back to the base to harass teammates more. I do not believe you can actually get out of bronze with an attitude like his, much less be matched in high plat/diamond. I looked him up only to find out he went from the bottom of silver to the top of plat in a matter of days. I just want to know where I go to submit his information for review. Thanks :P

http://i63.tinypic.com/2s84nbq.png[/IMG]

This player went lux toplane, went 0-3, then started harassing teammates and telling the enemy to shove and he wasnt going to defend.

Edit to add the lolking graph. This is not a discussion btw, I just want to know what the proper way to report this player is and Riot can determine the truth.