Not too easy. I was delighted when I found out it was possible to "distract" people like that. Making it harder would just encourage save/reloading to avoid pissing off the entire city. It's OK with a measure of predictability, especially in a turn based game.
If it absolutely MUST be changed, then make it turn based and require strategy for getting it completed. Requiring twitch reflexes for stealing in real time - in a turn based game - would be stupid.