When running a game, you should always take notes of what the PCs are doing. Ostensibly for record-keeping purposes.

But mainly so you can set up horrible, horrible consequences of the things that they do with nary a second thought.

Transcript

{Obi-Wan and Jango continue fighting}
Obi-Wan: Why are you doing all this? This elaborate plan?
Jango Fett: Why?
Jango Fett: Ha ha! Kenobi wants to know why.
[SFX]: Blam!
Jango Fett: You still don't know who I am, do you?
Obi-Wan: Jango Fett. You're some kind of bounty hunter—
Jango Fett: No.
Jango Fett: Jango Fett, private investigator.
Obi-Wan: Whu...?
Jango Fett: Of Maul and Fett.
[SFX]: Blam!
Obi-Wan: {horrified} Oh my god...
[SFX]: Blam!
Jango Fett: You.
Jango Fett: Killed.
Jango Fett: My.
Jango Fett: Partner.