Capitol police response team told to stand down?

Probe launched over claim that elite Capitol Police unit blocked from Navy Yard massacre

The board that oversees the U.S. Capitol Police has opened an investigation into whether a tactical team of officers that was one of the first on the scene during the Washington Navy Yard shooting was ordered to stand down.

The investigation follows reports that a highly trained and specialized Capitol Police team arrived soon after the shooting started, but was told by a supervisor to leave the scene.

The BBC, which first reported on the allegation, quoted a Capitol Police "source" as claiming "lives may have been saved" if the team could have intervened.

U.S. Capitol Police Chief Kim Dine said the force "offered and provided mutual support and assistance" on Monday, and that there is a "preliminary investigation into the allegations presented."

House Administration Committee Chairwoman Candice Miller, R-Mich., also said she's been advised "there is currently an active investigation into the allegation."

According to the BBC, the Metropolitan Police Department -- the police force for Washington, D.C. -- is denying the claims. One MPD officer was also wounded in the shooting.

But an official with the Capitol Police union said the Containment and Emergency Response Team (Cert) -- the tactical team in question -- trains for active shooter situations.

They reportedly arrived near the scene within minutes of the report of an active shooter going out and were armed with HK-416 assault weapons.