In the following hours, police searched for two other possible gunmen. By afternoon, one of those men was determined not to be connected. By that night, police were sure Alexis acted on his own. The FBI said the confusion possibly was a result of people with weapons in hand trying to stop Alexis.
Finally, they cleared the building. Workers left the yard and the reality of what had happened began to set in.
While investigators worked to put together the pieces of what took place on that horrific Monday morning, the Navy Yard complex reopened. But Building 197 remains closed. It could be weeks before workers are able to return to their cubicles and offices.
It will be even longer before their Mondays once again feel normal.