You have to stand next to his house (inside the wall of his complex). To get the /say to work you have to stand at the back of his house, where the chimney is ... but first you have to target him.
You should be able target him from anywhere outside the house (not just the chimney) with
just this:
Although:
should work too.
If that doesn't work maybe someone just killed him?
I literally was doing that camp yesterday so I'm
certain the above works.