LAWRENCE: I — killed — two people, I mean two Arabs. One was a boy — this was yesterday. … I led him into a quicksand. The other was a man — that was, oh let me see — before Akaba anyway — I had to execute him with my pistol. … There was something about it I didn’t like.

ALLENBY: Well, naturally.

LAWRENCE: No. Something else.

ALLENBY: I see. Well that’s all right. Let it be a warning.

LAWRENCE: No. Something else.

ALLENBY: What then?

LAWRENCE: I enjoyed it.

I killed two people yesterday

Robert Bolt (1924-1995) English dramatist
Lawrence of Arabia, Part 1, sc. 621-623 (1962) [with Michael Wilson]
    (Source)

The above is from the Bolt shooting script. The actual movie sequence has slightly different language and intonation in Lawrence's first line:

I killed two people, I mean, two Arabs. One was a boy. That was -- yesterday. I led him into a quicksand. The other was a man. That was -- before Aqaba, anyway. I had to execute him with my pistol. There was something about it I didn't like.