Bill Wallace?

If you grew up in Oklahoma like so many of us did, you were undoubtedly exposed to Bill Wallace at some point. He is (was?) a children's author from Chickasha, and wrote many of my favorite books back in elementary school... A Dog Called Kitty, The Biggest Klutz in Fifth Grade, and who could forget Danger on Panther Peak? But anyway, the whole purpose of this post is to find out if anybody knows if he's still alive. This whole curiosity began when I was doing random searches on Wikipedia, and the search for Bill Wallace brought me to the bass player from some band. I began to think about writing an article about him, since he was my favorite author as a kid, and thought that knowing whether or not he's alive would be a good thing. While the internet seems to make no mention of his death, so far as I can tell, he hasn't published anything since 2001, and I can't seem to find any current biography info. If anybody knows the scoop on this, and would fill me in, I'd really appreciate it.