Tryndamere Ult still Works When he is Silenced

I was playing a game of Aram using Garen . The opposing team had a Trydamere . I tried using a Q (Decisive Strike) silence on him, followed by Garen's ult to finish Trydamere. Instead Trydamere immediately uses his ult after my Silence, negating the ult killing blow. I used the same combo 6-7 times through the game and the same result. The Q was maxed leveled. I don't think it is network lag. My ping averages about 28.

Anybody else noticed this?