Ambush the guard

The opportunity is too good to pass up: a uniform, fully-loaded belt, and almost certainly some kind of useful key pass. If you can overwhelm the guard, you can assume their identity and move more freely around the ranch.

As the guard passes the brush you're crouching in, you grab their ankles, sending them toppling to the ground with a surprised noise. You lunge onto them just as they turn, dazed, but ready to defend themselves.