[GAMEPLAY] Warwick ult bug maybe?

I'm not sure if this is a bug or intended:

I was playing as Tristana. The opposing team's Warwick and I ult'ed each other at the same time. As Warwick lunged at me my Buster shot knocked him back. Warwick's Infinite Duress suppression ended instantly but the damage didn't stop.

Step 1: Have Warwick and Tristana Ult each other. Step 2: See what happens.