Later reports indicate the perp was a ex-employee of the TV station, who was disgruntled. I believe this means it is some kind of revenge shooting, but no one in the media or Law Enforcement has said that; I am simply guessing.
An ugly scene. The murdered cameraman caught an image of the assailant with gun in hand, whether accidently or deliberatly is unknown, but it's out there on the news on CNN & Fox. This will NOT help him if he's caught alive and put before a court.
A horrible event indeed. There is audio of the shooting.
My prayers to the families of the victims.