The tip received by police was vague, but potentially dire: a Pennsylvania physician was on his way to the nation's capital with a carload of weapons, planning to visit the president.
As a result, Bryan Moles, 43, of Edinboro, Pennsylvania, was arrested on weapons charges after checking in to the Trump International Hotel in Washington, a few blocks from the White House.
He is expected to make an initial court appearance Thursday afternoon.
While the Secret Service interviewed Moles and determined he posed no threat to the president or anyone else they protect, D.C.'s police chief said the tip averted a potential disaster.
"I was very concerned about this circumstance," Chief Peter Newsham said. When people come to the District "armed with those types of weapons, it's a serious concern. ... He doesn't have a really good reason for being here."
Moles was charged with carrying a pistol without a license and having unregistered ammunition. A police report said authorities seized a Glock 23 pistol, a Bushmaster assault-style rifle and 90 rounds of ammunition from Moles' vehicle.
Newsham added that the department does not presently have enough evidence to charge Moles with making threats.
Newsham declined to comment on what may have motivated Moles. He said he did not have a license to carry firearms in the District, which has strict gun laws. He did not know whether he was licensed to carry in Pennsylvania.