A man was found dead with a cassette recorder in one hand and a gun in the other.
When the police came in, they immediately pressed the play button on the cassette.
He said "I have nothing else to live for. I can't go on," then the sound of a gunshot.
After listening to the cassette tape, the police knew that it was not a suicide, but a homicide.
How did they know?
If the man shot himself while he was recording, how did he rewind the cassette tape?