investigators say that killer was wearing a mask and body armor when he opened fire with a modified rifle. one capable of holding magazines with hundreds of rounds. the police chief saying, if officers hadn't taken out the shooter before he got to that bar, the bar to which those crowds were running, the chief says it would have been catastrophic. hundreds of people in there. little comfort perhaps to those that today woke up without their loved ones. the latest victims of a mass murder in america. mike tobin reporting live. mike? >> shepard, this is where it all went down. it was just after 1:00 on a warm summer night. people were floating back and forth between the night spots here. with the video, some of it has sound. others you see people freeze for a second. wonder if it's real and then they panic and run. the gunman appears in his body armor carrying 250 rounds