At the same time though, they're what, 14 years old or so at that point? Trapping David may not have been the most logical thing to do, and may have been crueler, but from a young person's perspective (especially young people who've sometimes espoused that any life is better than no life - Rachel in #17, Marco in #5 and #10), I can totally see why they thought it was the better choice even though I disagree. While there may not be a rational difference, to humans there's an emotional difference between killing someone you know, whose situation is your fault, outside of combat, and killing someone you don't know as collateral in the middle of a fight.