Sigrid and Alvor of Riverwood just bit the big one, Alvor getting chomped and chucked like a ragdoll. Birna fell to one several game weeks ago in Winterhold. It's sad losing village folk, but worse when they're your merchants.

It happens, all you can do is load up a previous save.

Oddly enough, Alvor always seems to charge at anything in Riverwood. He's the first to die too.