Wow, very impressive. Never expected you would actually get a shot if it. My brother told us it was more likely a weasel and from images we looked up that seems to be true. And from how you describe its behavior.Had no idea there were weasels around here.
Great job on the photo. Thanks for posting it.
Thanks Sonja;
When I stopped by the same spot today, I knew that it wasn't someone's pet ferret. I thought that it was vey quick getting around all those rocks so fast, but there is more than one, in fact there are many. I seen four at one time along the rock wall. As shown in the last picture, if you look closely you can see three and there is another that is just to the left that is not shown. The picture is cropped so the quaility is crap.
So I think your brother is right, it(they) is not a ferret but of the same family, could be a weasel, fisher, or a marten.