Brandishing a gun by describing it in a note

In U.S. v. Groce, Judge Luttig concluded that the government met its burden of proof on the charge of brandishing a firearm in connection with a bank robbery, where there was evidence that the robber had the gun with her (even though no one saw it) and that she made its presence known by way of the note she gave the teller, which said, among other things, "I have a gun."