The Coast Guard has also made sure all of their recruiters around the country are aware of the incident and are on alert, Carr said. "Nobody comes into a Coast Guard recruiting station without an appointment, this is just normal policy," he added. Carr was checking to see if the offices had re-opened today.
All of the incidents -- two at the National Museum of the Marine Corps, one at the Pentagon, one at a U.S. Marine recruiting center and one at the U.S. Coast Guard recruiting center -- have a few things in common. They all take place in the middle of the night and seem to target military installations but not people.
As NPR reported, an FBI official speaking with reporters late last week seemed at times to be speaking directly to the shooter.
"We'd like to know what this grievance is and what we can do to try help resolve it," said John Perren, head of FBI's Washington field office. "We're willing to listen to him and hear his side of the story."
Investigators have a rough psychological profile of the individual. They say he is most likely (but not definitely) male, and could be a current or former service member who suffered a setback such as a divorce or a job loss, NPR reported.