Tragedy In Denton Texas

The Police are seeming to be engaged in what looks like a questionable arrest an assault of an African American Woman. To make matters worse a passer by sees this. And tries to talk some sense into the Officers, but his attempt only has him on the receiving end of what looks like a gunshot wound.
Sure Being a Police Officers comes with it's own brand of concern. But with the multitude of videos surfacing putting the Police in a bad light with questionable arrest procedures that ultimately show the Demise of an innocent, defenseless,  and UNARMED AFRICAN AMERICAN.When does an Officer's conduct become criminal?