Tryndamere gets killed during his ultimate with Brand's Sear

As the title says, Brand can or at least did kill Tryndamere during his ultimate with Sear. Well at least the kill screen said that it killed me 3 TIMES. Yep, I got killed with Tryndamere 3 times(ranked ffs) during my ultimate(cool downs followed every time), unless Undying Rage became 0.5s(the hidden cast time) then it's kind of champion braking bug. Even the guy playing brand felt sorry.