The US government will seek the death penalty for the accused gunman who killed nine people at a church last year in Charleston, South Carolina.Dylann Roof, 22, faces both state and federal charges that he massacred nine African-Americans after joining them at a prayer service at Emanuel African Methodist Episcopal Church, a historic black church in the coastal city of Charleston.Roof, who is white, had avowed racial hatred prior to the shooting."Following the department's rigorous review process to thoroughly consider all relevant factual and legal issues, I have determined that the Justice Department will seek the death penalty," Attorney General Loretta Lynch said Tuesday. "The nature of the alleged crime and the resulting harm compelled this decision."State officials had already said they would seek the death penalty for separate state murder charges.Most death penalty cases in the United States are heard in state courts, where the vast majority of violent crime is prosecuted.