A man who mailed packages containing an explosive device and a powdery substance labeled “Anthrax” to the 4th U.S. Circuit Court of Appeals in Virginia pleaded guilty and was sentenced to life in prison without the possibility of parole, prosecutors said.

Rodney Curtis Hamrick, 41, assembled and mailed an improvised explosive device in a manila envelope in October 2005 while being held at the federal prison in Leavenworth, Kansas, U.S. Attorney Chuck Rosenberg said in a statement.