Obama's newest famous quote is "I'm really good at killing people" — but what was the context?

The Daily Mail cherry-picked the quote out of the new book "Double Down: Game Change 2012." The book's not out for normal people until tomorrow. (Buy it here.) So I'm stuck wondering. DM says:

A Washington Post report makes passing reference to the anecdote, saying that while speaking with his aides about the drone program Obama bragged that he was 'really good at killing people.' The Obama Administration has not responded specifically to reports of the alleged boast from the President.

The Daily Mail is punctilious enough to say "alleged" but can't resist characterizing the words as a "boast." We're told he "bragged." The headline says "President Obama joked...." Let's assume for the purposes of discussion that Obama really did say those words in that order. But let's try to imagine why he might have said that.

Perhaps you're imagining a childish man, exclaiming "I'm really good at killing people" like a numbskull teenager playing a first-person-shooter video game. Or maybe you're picturing someone more like a movie super-villain in his vast underground lair, cackling to his fawning minions as he creepily caresses his "kill" button.

But it's possible to think of a context in which Obama would be sympathetic. I could imagine a serious discussion of the lack of genuine accomplishment in his administration.

O: What will history say we have done? Nothing! I was the embodiment of hope, and everything I have touched has turned to ashes.

AIDE: But, sir....

O: What are the accomplishments? Name the accomplish of the Obama administration! What will people say?!

AIDE: He killed bin Laden.

O: A pathetic, isolated idiot sitting in his hovel, watching bad porn. The SEALs blew him away. That was really amazing of me.

AIDE: [Names several significant terrorists who have been killed through the drone program.]

O [sadly, sarcastically]: I'm really good at killing people.

Intent on writing this little dialogue, I searched for a list of 4 or 5 good names for the aide to tick off in an effort to bolster the President's spirits. See if you can do that. I couldn't do it. I kept running into "A List Of Children Killed By Drone Strikes In Pakistan and Yemen." Go there. Scroll through those names (and ages) and think about that context and why Obama might have said I'm really good at killing people.