Rottweiler on the loose

We decided to do this small quick run before our upcoming 10K on Sunday. A small one. Maybe 3 miles. So we take Maggy along. Its dark and its cold! So the base layer and ear muffs and hats are on. We were on Monument, just behind Safeway and Madhura stops in her heels. "There's something rustling there", she says. And sure enough, there was this Rottweiler rustling in the leaves. No leash! We froze right there when he looked at us. I don't know if it was the dark or the cold, but I could feel the hair on my back raise. Imagine this 'thing' staring at you:

We did not want to take any risk to check if it was homeless or whatever!
For this one time, we were of the same opinion - Turn around! Both of us slowly moved back and headed straight home.
Strange Maggy did not sense him. Maybe he was just a lost puppy. But we were just not up to it. Though Madhura did call the ASPCA as soon as we got home to report a dog on the loose.
Now I know what I want when we get our own home with a yard. A Rottweiler. Yes sir! The effect it had on us, I want that exact same effect on any intended prowler.