Had a Heinz 57 like that once. Guy came up the driveway towards our youngest and Scooter did the same as yours. Got in between and growled. Not long after, someone poisoned him. One place we lived, before his demise, a sheriff deputy came into the cluster of houses we lived in to serve a warrant on someone. The dog was out roaming the yard and approached the ‘stranger’. Deputy stomped his foot at the dog. Dog moved in a little closer. I had to call him in the house. Fearless damn dog.
Some dogs are loyal and fearless like that. I feel lucky that I had one once in my life. I like my little terriers because nothing gets past them. They raise the alarm way before I know anybody is around. That gives me plenty of time to grab the .38.