User blog comment:Starmoonie/Can someone explain?/@comment-4568327-20140921025750

Maxis did not intend for babies and toddlers to die, but children and older can indeed die. The issues with the Witch Doctor and Bigfoot showing up look more like something else caused them to appear, which is usually corruption of some sort. Babies and toddlers cannot normally die in-game, so if they do die it's usually because of a game glitch or a badly-made hack. However, if you delete the graves of any Sim without No Unlink on Delete installed, it will corrupt your neighborhood.