That's not the point of the game, but people can do it.
The reason these horrible things can happen in The Sims is exactly the same reason they happen in GTA: these are cutting-edge video games defined by player freedom rather than locking the player into a prescribed narrative loop where veering off the racetrack means "lose" rather than "find a new adventure." When you give players the option to explore their fantasies, you're going to get some dark stuff. Yes, it's disturbing. But it's also the foundation of great art.
Annalee Newitz (firstname.lastname@example.org) is a surly media nerd who has just started playing GTA4 but has already read all the spoilers for it.