I found Galen still alive with Kasey standing near him.
I put Galen up on a 1 tile wide ledge I make in my 2 story high greenhouses to get him out of the way of Kasey. But Galen poofed away and I found them together.
The next second it was just Kasey and Galen's tombstone.
Then there was just Kasey
Since there are so many gnome tombstones scattered all over the lot, I moved them. I couldn't think where to put them at first, then I remembered that 1 tile wide ledge I put around the first floor of my 2 story high greenhouses.
I decided to move all of the gnome tombstones up there. I made it a stone floor instead of the usual wood and placed all 42 gnome tombstones up there.
I noticed they are each worth approximately 1500 simoleans.
BTW I put that ledge up there in my greenhouses to make it easier to place the windows.
Now I'm going to unleash some other gnomes in this garden and watch Kasey to see what happens to him. The only other gnome I have at the moment is that Magical Gnome of Invention one of my Sims has in his inventory. But I will now plant some plasma fruit so I suspect there will be vampire gnomes around soon too.