everything they see, everything they find is a data point they put into a computer program. they are re-assembleing a model of what they think what happened. early in the morning in the 8:00 hour as we've talked about, the shooter drove up, showed his i.d. walked inside, was carrying a bag. video under surveillance shows him going into a bathroom on the 4th floor. he emerges with a shotgun at the ready. >> it seems like he assembled it. >> you can do it in a minute of ten second, a recommendington, comes out very early on. they believe he had an encounter with the security guard and took his 9 millimeter shotgun. >> that is you talked of one of the victims earlier, mike ridgell. >> that's the second one. >> most of the carn allegeling they believe though was done from an overhang on the 4th floor. can you look down and started firing down into the crowd down there. now the d.c. police said they