Where's The Lead-In

Some conservatives are using this video showing a male police officer punching a woman in the face as "proof" that blacks in America are completely unhinged.



My first question, as always when presented with specious video evidence such as this, is where's the lead-in to what's shown in the clip? Why were these women stopped by this officer? If this really was a jay-walking incident, then how did it escalate to such a heated and physical exchange? There's much more to this story than what we are being told.