whats up with the champion deaths?

After going to the lol website i noticed some animated pics of Garen/Sona/VI/and Zed and to what i have noticed or found out is that it appears that they have been shot down by none other then jhin the new champ. and i was wondering if anyone has any insight on this because i love the lore and story background of this game and i would like to know how this all fits together thank you