The Demon Chimp

Alex Grisham comes back home from work one day and discovers something very strange. On the dining table are a scattered pile of papers that his pet Chimpanzee has typed on with the typewriter. Of course, they are all filled with meaningless nonsense. Just as he is about to get rid of the papers, Alex accidentally sees, in the midst of one of the papers the following words:

"I am going to kill Alex. I shall never be blamed for it for I am only a chimp."

He is stunned and baffled, unable to understand how that sentence got there or how the chimp could possibly have typed those words even by accident. Surely this must be the result of a prank played on him by someone who had somehow gained access to the house in his absence, and someone who knew about his chimp's habit of banging onto the typewriter.

But was it really someone else that typed it?