Boyd said the suicide vest that the suspect allegedly sought to use and had in his possession "had been rendered inoperable by law enforcement and posed no threat to the public."
The arrest, according to Fox News, took place at the corner of Pennsylvania and Louisiana Avenues in D.C.
U.S. Capitol Police Sergeant Kimberly Schneider said in a statement that the arrest "was the culmination of a lengthy and extensive operation during which the individual was closely and carefully monitored." She said the Capitol Police were "intimately involved in the investigation" and the public was never in any danger.
FBI agents had arrested another man back in September for allegedly plotting to attack the Capitol with remote controlled airplanes.