Another round of shots were fired overnight at the U.S. Marine Corp Museum in Triangle, Virginia, the fourth such incident the past two weeks.
The first three incidents, at the museum, at the Pentagon, and at a Marine Corps recruiting centre, were all linked by a single gun. It is unknown whether this fourth shooting is linked.
All previous shootings were into portions of the facilities that were unoccupied.
The Pentagon is ramping up security in response to the attacks.
This video covered the attacks up to the overnight shooting, which may be related to the other three.
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