3rd Riddle!

Heyoh! None has solved my 2nd riddle! The ans is SPONGE, with holes everywhere bt still can keep water. Haha.

Now here comes my 3rd riddle!

Question:

Suicide or not?

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 entered the room and pressed the play button on the tape recorder they heard..."I can't go on. I have nothing to live for." Then there was the sound of a gunshot. How did the detective immediately know that the man had been murdered and it wasn't a suicide?

This is interesting... needs some thinking.

Love, YIN...