Anderson Cooper 360

AC360 411: Ricin’s Wrath

Editor’s Note: We’ll have the latest developments on the ricin investigation tonight on AC360° at 8 and 10 p.m. ET.

Suspicious mail laced with ricin has Washington on edge. Preliminary testing shows a letter addressed to Pres. Obama and another to Mississippi Republican Sen. Roger Wicker both tested positive for the poison at off-site mail facilities.

Additional testing on the letters should be complete on Thursday. According to a law enforcement source, both letters had the same message: "To see a wrong and not expose it, is to become a silent partner to its continuance. And the same closing statement: "I am KC and I approve this message." Here’s the AC360° 411 on ricin: