In the Twilight Princess Ganondorf murdered a sage. Plus judging by his personality he definitely has done so in the past.
After you recieve the Ocarina of Time, but before pulling the Master Sword from the Temple of Time, there is a guard in the alleyway closest too the Castle, he is injured from Ganondorf's attack on Hyrule Castle, after telling you too save the princess, he dies. I don't know if Ganon killed him or not.
It's also implied that he killed the King of Hyrule in Ocarina of Time. He also killed the Great Deku Tree, if that counts as a 'someone'.
He can murder Link if you aparrently suck at his battle.