The FBI doesn’t seem to have much faith in the competency of the ATF:

Within hours of the Navy Yard shootings, the FBI had traced the gunman’s recent shotgun purchase and sent agents to the shop in northern Virginia where he bought it. Left out of the loop was the Bureau of Alcohol, Tobacco, Firearms and Explosives, a surprising snub between top U.S. law enforcement agencies that comes as the ATF struggles to show its relevance in Washington.