A U.S. Capitol Police emergency team was sent away from the Sept. 16 mass shooting at the D.C. Navy Yard due to traffic and the potential for a secondary attack on the Capitol, a review by Capitol Police found.

The review was ordered to look into the reason why the response team — just blocks from the Navy Yard — was told to stand down and then return to the Capitol.

Capitol Police said Friday that multiple sworn personnel self-deployed to the Navy Yard area, but a four-person Containment and Emergency Response Team (CERT) — which has experience and training for such incidents — had trouble getting to a command post due to traffic caused by both emergency vehicles and commuters.