I forgot that Poolman would be here today. Tyga was in the backyard, and as soon as I heard him barking I realized what was going on. He went into guard dog mode, and did exactly what he needed to: alert me to an 'intruder' in the back yard.
I told him he was a good boy, but then brought him inside, where he continued to monitor said intruder through the window, growling softly. Once the man finished and was leaving, I let Tyga out again, whereupon he stood by the gate and (quietly) watched the man head toward his truck.