He was going to blackmail you. So you killed him, too.
5 seconds sound clip from the After the Thin Man (1936) movie soundboard.
You can hear this line at 01:47:06 in the DVD version of the movie.
Quote context
[...]
- But look at that picture. There he is, 6 years ago... And his mustache is neither long nor white.
- You didn't notice him 6 years ago any more than I did.
- You remember him as you saw him last night, when you shot him.
- You killed him, and then you killed Robert.
- Phil saw you do that. That's why he followed you. That's why he was on your fire escape.
- He was going to blackmail you. So you killed him, too.
- And then you threw that note into my window, hoping to throw me off your trail.
- David, say you didn't do it!
[...]