Quote from : Star Wars: Episode III - Revenge of the Sith Movie

Supreme Chancellor: [Anakin cuts off Dooku's hands ending the battle. Anakin catches Dooku's lightsabre and ignites it and puts both lightsabres to his neck] Good, Anakin, good. Kill him.
[Dooku looks at Palpatine in shock]
Supreme Chancellor: Kill him now.
Anakin Skywalker: I shouldn't...
Supreme Chancellor: Do it!
Anakin Skywalker: [Anakin decapitates Dooku] I couldn't stop myself.
Supreme Chancellor: You did well, Anakin. He was too dangerous to be kept alive.
Anakin Skywalker: Yes, but he was an unarmed prisoner.
[frees Chancellor Palpatine]
Anakin Skywalker: I shouldn't have done that. It's not the Jedi way.
Supreme Chancellor: [stands up, rubbing his wrists] It is only natural. He cut off your arm, and you wanted revenge. It wasn't the first time, Anakin. Remember what you told me about your mother and the Sand People.
[sound of sand people screaming in as if Anakin can still hear their death]
Supreme Chancellor: Now, we must leave before more security droids arrive.