Hi @str8ttodvd thanks for reading The Fan. Hope you don't mind but I had to delete your comment, only because you left it right at the beginning and it contained a spoiler for any new readers. But in answer to your question, Kyle was suffering from extreme paranoia fuelled by his drink/drug addiction and the fear of being stuck in the lift with the fan. He killed her because he was terrified and convinced she was going to hurt him. Hope that helps!