i dunno that seems legit.

you try and hit him with a silence spell. based on the opening battle speech, he's egotistical as all hell! he mocks what is probably the most worthless spell in your arsenal and is offended on a personal level. due to that, he just starts rambling like Billy Bob Thornton in Sling Blade. since going into the fight there is a pretty good chance he still likes oxygen, his incessant end of MGS2-esque rambling causes him to drown in Walze Tower.

that's why you get the tiger mask AND the shard. you outsmarted him the other way.