Didn't watch but the press conference was apparently an embarrasment. Sherriff is pretty nutso. Was pissed that people were upset that the arrest wasn't made earlier, pounded his fist on the podium, quoted hateful comments the department recieved including the n-word. Basically bitched for the entire first half of the press conference.
As far as the case, they put together the story from all available video and a bunch of eye witness accounts. McKnight cut off Gasser, Gasser got road rage and started chasing McKnight in his car. McKnight notices and parks his car and gets out to confront him for said road rage. Gasser kills him because he felt threatened by McKnight's words. Also, there are reports that Gasser yelled at the dead body of McKnight after the shooting, which could've have caused the confusion of the initial false witness account that said Gasser stood over McKnight when he shot him.