The protagonist gets into the elevator on the first floor to go up to his office. He isn't paying attention when the antagonist gets in the lift.
After a few seconds the killer starts a conversation between them about how one of the managers had an accident and had to leave. The protagonist quietly notices a blood mark in the elevator asks the killer what happens and he said he doesn't know.
When the elevator gets to the 12th floor the killer shows a knife and says he is going to kill him on the next floor up.