WARNING: Article Contains Footage That Some Readers May Find Distressing
The muscular pit bull was captured on customer Michael Ray's doorbell camera at his home in Las Vegas, Nevada, when it seemed to wander out of nowhere towards his daughter - named Lauren - who, at first, gently stroked the dog and greeted it.
But things took a very dangerous turn when Lauren's own dog, Max got involved, resulting in the pit bull attacking both of them.
At one point, the pit bull appears to pin Max down with his jaws clamped around the smaller dog's neck.
The Amazon driver appeared to arrive at the scene very shortly after the attack began and with unbelievable bravery, she stepped in front of the savage dog to allow Lauren and Max to get to safety.
She is heard shouting: "No, no, no, no! You're a bad dog!"
Michael, who was out at work at the time, said of the incident: "My Ring (doorbell camera) alert went off and I watched the entire situation unfold in front of me.
"She [the driver] could have easily stayed back, she saw how aggressive the dog was, but came flying in to help without a thought of her own well-being."
The pit bull's motive to attack Lauren and her dog remains unclear, but it appears that the dog was either a lost pet or a stray.
Michael shared his amazement over the driver's heroic actions in a Facebook post and said the moment the driver tells the pit bull it's a bad dog is 'classic'.
His family was able to locate the woman to thank her with a bouquet of flowers, according to local news outlet KVVU-TV
One YouTube user felt the driver deserved more than a bouquet and even called for a pay rise.
Others, however, criticised Lauren for petting the aggressive dog in the first place.
Johnny Schist said: "Why didn't she just go back in the house. Also her little white dog seems to be the initiator of the confrontation.
"The other dog has absolutely no aggression towards it until the white one starts up. Also seems like no aggression towards people."
Amazon has been contacted for a comment on the incident.
Words by: Charlie Metcalfe