Gameplay. Tryndamere dies while in ult

While playing tryndamere, I press ult while diving. I hear the scream. the ult goes on cd. And within a second... i die. I main trynda.(152k mastery) and so i noticed this happens more often then it should. about 4 times now. I dont quite know how to re-do this. but I think its a matter of a "close call" between dying and ulting. as a link i posted the game hystory. happend around 24:50. (dont know is this will help)

ps. No its not that i just ulted to late.. (people always rage that)... the ult goes on cd.. and i hear the scream..(not the spinscream). so that means is has been activated