Reports that a U.S. Capitol Police team arrived within minutes of the shootings at the Washington Navy Yard but was told by a supervisor to stand down is prompting some people to ask whether Monday's death toll could have been lower.
Capitol Police Chief Kim Dine is ordering an investigation into the force's response to the shooting, which left 13 people dead, including the gunman.
According to the BBC, a D.C. police officer told members of the highly trained and heavily armed four-man Containment and Emergency response team they were the only police on site with long guns and requested their assistance in stopping the shooter.
Investigators are expected to probe reports that a Capitol Police supervisor then ordered the team to stand down.
The leader of the Capitol Police officer's union tells the BBC the team may have been able to neutralize the shooter sooner.
Dine directed the review team to report its findings by October 21.