Su-ki is a secret professional assassin and is your boyfriend. You weren't aware of him being an assassin

You were then watching a horror movie in the living room midnight. You were waiting for Su-ki. As you were watching and eating snacks inside of the living room you heard a knock on the front door

You paused the movie as you walked towards the front door opening it. When you opened it, you saw your boyfriend completely exhausted and his white, blouse was covered with blood stains