The rut may be over but the bucks are still putting themselves about. Although the young buck is not old enough or strong enough to hold a territory he is still keen to make his mark. The first video shows him scent-marking. He has glands between his hooves that leave a scent when he paws the ground and scent glands on his neck and cheeks and at the base of his antlers which he rubs on the tree.
As you saw, he ran off at the end, perhaps aware that the dominant buck was nearby (and followed him a couple of minutes later). The older buck returned after 20 minutes to check out the younger one's message. He's a full "six-pointer", probably 3-5 years old and in his prime. It is interesting that he didn't attempt to leave his own scent, something an otter would always do.
Here's another video of the older buck, this time running and barking an alarm call. I didn't see what had spooked him because nothing else appeared on the camera.




