The F.B.I. on Wednesday arrested a Navy veteran suspected of sending two envelopes to the Pentagon this week that contained raw materials for the deadly poison ricin. The man, William Clyde Allen III, was detained at a home in Logan, Utah.
Two envelopes addressed to Defense Secretary Jim Mattis and to the chief of the United States Navy, Adm. John Richardson, set off alarms in a mail screening facility outside the Pentagon on Monday. No one was injured.
