Hmmm, I looked up sheild bug images. They are also called stink bugs and look very "prehistoric" with armour looking backs, longish legs and are quite a bit larger than a bedbug. I've seen them outdoors before at my home. The OP's photo looks much different to me. Its shape reminds me of a bedbug, but I can't see any legs to confirm. I've seen four bedbugs on various caminos and I always describe them to people as looking kind of like an apple seed in size, shape and color, but I'm no entomologist either.