Bug from the First Herald Quest ACT4

Hi GGG,

Just want to report a bug from ingame quest. I killed the First Herald in ACT 4 the same time as I was dead. Then I respawned and walked back to fight the boss again but yet the boss started the dying animation and then disappeared. The quest then doesnt allow me to progress as It says for me to confront Kanu and First Herald but then the boss and Kanu wasn't there. Please help !

Bug Report ID: #3526153101