Steven Albright: A silencer.
Natalie: That would explain the gunpowder and the duct tape.
Steven Albright: Who would use a silencer to kill himself?
Natalie: Okay, Mr. Monk, what are you saying? Are you saying Commander Whitaker?
Steven Albright: What about the locked door and the gunshot?
Adrian Monk: I don't know how he did it. I don't know why. But he's the guy.