Ridgeway, 35, of California, has pleaded guilty to voluntary manslaughter and attempted manslaughter.

CNN: Blackwater defendants plead not guilty

Five former Blackwater security guards pleaded not guilty in January to charges of voluntary manslaughter and other serious crimes stemming from their involvement in the September 16, 2007, incident in a Baghdad square.

CNN: Blackwater founder, CEO resigns

Earlier this month, five former Blackwater security guards pleaded not guilty to charges of voluntary manslaughter and other serious crimes stemming from their involvement in the September 16, 2007, shootings in a Baghdad square.

CNN: Official: U.S. will not renew Iraq contract with Blackwater