The murderer picked up the gun where Yvette dropped it, ran to the door, opened it, recognized the girl from her photograph, shot her, and then ran back to the cellar.
8 seconds sound clip from the Clue (1985) movie soundboard.
You can hear this line at 01:24:35.627 in the Blu-ray version of the movie.
Quote context
[...]
- One plus two... Plus one... Plus two... Plus one is...
- Ran to the library, hit the cop on the head with the lead pipe.
- Then, coming out of the library, the doorbell rang. It was a singing telegram.
- Yes.
- But Colonel Mustard wasn't in the cellar.
- So?
- Don't you remember your fatal mistake?
- You told us at dinner that we were eating one of your favorite recipes.
[...]