It happened right in front of their very eyes....
This is a legitimate question...
If the police saw a shooting on the street, a murder, would they act then and detain the shooter? Or go back to the station and file a report?
does this have nothing to do with "the blue wall of silence"...."us vs. them" attitude?
I'm not going to teach police process 101 to you. If you are that clueless, so be it. Go ask a lawyer to explain it to you or something.