Grave markers in someones garden edge , North Seattle

 Not sure why these are here- well I realize they are delineating a garden edge  outside a rather posh home , but where did they come from?
Seattle has such a strange and lurid cemetery history.
Moving Cemeteries and not moving the bodies , you know the kind of thing that harkins back to horrors induced from watching poltergeist as a child for the first time.
Anyways are these victims of such circumstance?
Or did someone just suddenly not need them?
anyone?