Zed's story question

alright i was reading his story due to him being one of my main's and noticed something strange - The dark ninja followed the master inside. Moments later, the assembled ninjas heard Zed cry out in pain. Mysteriously, he emerged unscathed, and threw the severed head of the master at Shen's feet

why would zed cry out? riot was he not himself when he killed him and cry'ed out after seeing what he'd done? please reply riot<