If he hasn't been on your property before and just showed up now, I wonder what caused him to relocate? A bigger and/or more dominate buck took over his home range, or he found a better spot to call home? It's strange for mature bucks to be relocating, especially during the fall.
We have the exact scenario playing out at our place and are trying to figure out what the reason(s) could be. Coincidentally, our biggest and most mature buck has virtually disappeared since the new buck showed up.