For a start, I'm sure there are a lot of guys named "Kevin Smith" in Buffalo, NY. How about an email address or Facebok page so we know which one you're talking about?
Where does he advertise? Here, Facebook groups (if so which ones?), Kingsnake, FaunaClassifieds, or ?
If he's a member of this forum or other forums, what is his screen name?
What snakes did you buy? How many? How long ago? How long did you have them before they showed signs of illness or they died?
Did you take the snakes to a vet? If so, what was the diagnosis and treatment?
If they died did you have a necropsy done? If so what were the results?