Other than the business with the ceiling tiles, there really isn't much else you can do to conceal what happened. People aren't generally bashed into the head by accident.

That being said, the ceiling tiles could work. You'll want to be careful with the details, though - plaster in the hair, smear of blood on the chosen tile, that kind of thing. Jogging a few extra ones loose would also help - verisimilitude and all that.

Shelley doesn't hear anyone coming, yet.