Clay faltered for a moment upon seeing the person that lived with him for so long dying in front of him. He felt impotent before Dean's new power. He never would dream that the boy had become so strong in such a short span.
He watched in a daze as the head of his friend rolled on the ground.
Just after a lot of time did he get to know Kevin enough to empathize with him. Just after several years of living, going through trials and struggles, did he see Kevin as a friend.
Clay learned to give importance to him, and to all the others that went through adventures with him until that day. He just didn't realize how much they meant to him, not until that point when he saw one of them getting killed.
It was hard to accept when someone you knew for so long just died in front of you. It didn't seem real. No matter how much he tried to absorb the situation and react in time, he couldn't. It was just too much for him to take.
