A man was found dead in his study. He was slumped over his desk and a gun was in his hand. There was a cassette recorder on his desk. When the police pressed play on the tape recorder, they heard, "i can't go on. I have nothing to live for." Then the sound of a gunshot. How did the detective immediately know the man had been murdered and it wasn't suicide?
If he had shot himself the police would have to rewind the tape before pressing play to hear the message? Someone else must have rewound the tape after killing the man.