You gotta get your story out, right away.

After any of these terrible confrontations between citizens and authorities (cops), there are always TWO stories.  There is the victim's story, and there is the authorities story.  There will always be some differences, which can cast the entire incident in one light or another.  For example "Hands up don't shoot", which the Michael Brown supporters claim happened vs the cop's story that Michael Brown was trying to grab his gun when he was shot. 
  Moral of the story, the authorities must get their story out, right now.  Even better if they have video to back up their story.  They need to know that the other side will get their story out, and when there is only one story out there, that's what people believe.  So the authorities must get their side of the story out, right away.
  Lots of cops and prosecutors complain that releasing a story ahead of the trial does bad things for their case at trial.  Piffle.  The real trial, the one that counts, is the trial by public opinion.  If the public thinks the authorities behaved badly, it doesn't matter what a judge declares, usually years later.  The lawyers have so degraded the American justice system that it doesn't really matter any more.  Today's courts take years and years to come to a decision, and they usually let the perp off.  Better to win in the court of public opinion than wait for the wheels of justice to get turning. 
   Historical example.  Right after the Battle of Bunker Hill, the Americans wrote up their story, emphasizing patriot heroism and really stunning Redcoat casualties.  The rebels got their story onto a fast Yankee schooner and it was in London within three weeks.  General Gage on the other hand, sent his dispatches back on a slow Royal Army merchantman which took three months to get to London.  Result, the American version of the battle, with it's story of Patriot bravery, went the length and breadth of England for two and a half months before the British side of the story got out.  Needless to say, the American version, so favorable to the Patriot cause, is the one every Englishman heard.