The Warden's eyes were wide open as he was stunned at the sudden turn of events. However, he was not actually killed as Ameel's intervention made Verone leap backwards leaving the arrowhead sticking out of his chest with the tip just barely piercing his heart.
He was revealed for exactly one second before his eyes turned bloodshot and he let out a guttural scream.
When Verone stabbed him, he furiously pumped killing intent into his body. So, even though the Warden was not dead, with the pain and insanity filling his body along with his mind he certainly wished that he did.