I could have just called the police, but that doesn't really help in an immediate situation of one person trying to stab someone. So this situation calls for either: 1) Subduing the attacker by pinning them. 2) Doing enough damage to the attacker that they can't move. If they are on top of the victim, they maybe are in a good position for me to run up and corner-kick their head and end things with a quick concussion. I can't tell from the prose. Otherwise, it would be better to just restrain her and pin her to the ground.
So I'm either a man pinning screaming woman to the ground in a public place or a man who is viscously beating a woman in public.
No thanks, "Real Men" don't hit girls. http://goodmenproject.com/featured-content/brand-what-do-you...
Especially not in public where "defend the woman being attacked" is a fantasy for a whole bunch of people.