It was reasonable for officials to reroute a Capitol Police tactical squad away from the Washington Navy Yard rampage amid concerns about possible threats to the U.S. Capitol after the officers got stuck in traffic, according to a report released Friday that defends the decision.

The officers in the specially trained unit, which handles crises such as mass shootings, tried to respond to the Navy Yard but could not even reach the command post there because of traffic snarls caused by emergency vehicles, according to the two-page document. There were also no demands for additional Capitol Police resources beyond the teams that were already there and commanders were faced with “the potential of threats or secondary attacks” to the Capitol building, the report states, according to an Associated Press story in the Washington Post.

The unit was directed to the Capitol more than a half-hour after the first reports of the attack.