Multi accounter report

I'm playing in an American homefront map (398202 with some of my alliance members. One of us has noticed that one of the players in the game, was cheating by mult-accounting. Here is some proof. Openly admitting to it. Besides this, he also made a coalition with said 3 accounts. (see attacked image) I'm also suspecting that he's using 1 device per account, as per account it's either 100% played on PC or 100% played on mobile.