The official says the packages contained black powder along with rambling, nonsensical notes similar to those the man has been known to send in the past. The official spoke on condition of anonymity because the official was not authorized to speak publicly before an official announcement.
Authorities did not name the man, but said he was known to law enforcement.
Roughly a dozen sites received packages Monday, including Joint Base Anacostia-Bolling in the district and at Fort Belvoir, in Virginia. No injuries were reported, and the FBI said each package was collected for further analysis.