Federal authorities have arrested a man identified as Paul Kevin Curtis of Tupelo, Mississippi, in the mailing of letters laced with toxin to President Obama and Sen. Roger Wicker, reports the Clarion-Ledger. Not much is known about the suspect at this point, though both letters were signed, "I am KC and I approve this message." Each also contained the message, "to see a wrong and not expose it, is to become a silent partner to its continuance."
The letters were flagged at mail-sorting facilities before reaching their intended targets. Initial tests turned up positive for the poison ricin, but NBC News reports that it's still not clear just how potent the letters were. Further tests are under way. The letters were postmarked on April 8. CBS News says there were three in all, one to Wicker, one to Obama, and one to a Mississippi justice official. (Claire McCaskill had previously said that a suspect identified in the case was known to be a prolific letter-writer to lawmakers.)