when my wife and i were dating, i was involved in a good samaritan situation where a similar thing happened.
New Years eve, prob 1998'ish, stopped at a supermarket b/f a party. checking out and hear commotion from the exit area. Security guard is holding a woman as shes beating on him. Another guy comes in from outside and starts beating on guard. He's looking right at me yelling for help. No one else in store so i run in. I grab the girl as he deals with the guy. I have the girl from behind and she is throwing elbows at me. So i decide to hip toss her to the ground. She was wearing one of those old Starter sports jackets and when i put her down, she slid right out of it along with all the groceries she was shop lifting. She jumped up and to my surprise (as well as my GF and the cashier looking on in stunned disbelief) she was nude under the jacket....aaaaand it wasn't pretty. She starts throwing punches at me, while the beewbs are swinging wildly in the opposite direction, i didn't know what to defend. So i just put my shoulder down and tackled her to the ground and held her down, thankfully the cops were not far behind.