usage of as and have

When I was reading a novel by Steinbeck, I have met the sentence below:

"He stalked her then, game-wise, as he had the woodchucks on the knoll when day after day he had lain lifeless as a young stone and watched the old wary chucks bring their children out to sun."

I am confused a bit.

Do "…as he had…" mean "… "as if he was watching…"? Would you please explain the grammatical structure in that sentence!

Thanks so much!