Shadow's assassin calmly opened the door. He had already regained his composure after being able to unleash his fury moments before. At this time, he just wanted to enjoy catching his prey. Which was easy enough because the room she had fled to was actually a locked room, with no exit for her to escape. So there was no need to rush. He wanted her to think that she had any chance of escaping, only for her to fall into despair afterward. That was the real goal of the Shadow's assassin. It was indeed quite cruel and inefficient behavior for an assassin.