In looking at that situation, I would say 18 inch pump 20 gauge would have been the best because its a solo lady so easy to handle. Definitely buck shot, a round to the face would have chased him away. No aim necessary.
Now for dudes up there, here are some Pro Tips:
In the USA wear folks wear winter clothes, so Im a fan of more traditional hollow points or even FMJ in .45 or 10mm because you need penetration through the clothing layers. Here, no shirt country, I would love to try out a .455 Webley, a round designed for shirtless or jibba wearing natives by the Brits. I used to load 260 grain lead at 650 fps which hit pumpkins like a frieght train, bet ya it would knock the speed freak out the door. Bet ya there are a ton of Webleys floating around out here. Or even an old WW1 Smith and Wesson.
Or, my personal favorite for the scared of guns crowd...hockey stick. Hockey sticks are the great equalizer and can be sawed off. Its almost like an Algonquin war club. Try it at home, gentle readers, its Pumpkin Season