I cannot think of anything sadder than being picked off by a serial sniper.  
Becoming the victim of a regular serial killer, messy as the death might be, at least allows you a screaming, kicking chance.  Being shot dead as you gas up the car or push your grocery cart across the parking lot may be a faster way to die, but it doesn't give you the opportunity to look into the killer's eyes and choose to die a warriors death - fighting like a wildcat and screaming like a banshee.  No one ever knows how they might react when put into a crisis situation, but unless the killer had a gun to my kids' head (in which case I'd be simpering putty in their hands) I fervently hope that with my last breath I would give my assailant some serious wounds to lick when he got home.  But with a sniper....hell......you don't have a chance.