1) The dog was stressed and/or 2) The woman reached for the dog's tags/collar and the dog reacted to correct what it perceived as a threat reaching for its jugular.
In any case, the woman was sufficiently *not* afraid of the dog to be willing to follow it and make sure that both it and others were safe.
Unfortunately, the agents of the state lacked her goodwill.
"Pitbull" (Known to anyone with an IQ above room temperature as a "Shar pei".)
Clearly, a vicious dobe in Shar Pei clothing. (Getting stealthy, those dobes are).