After filing the court documents on Thursday, South Carolina Solicitor Scarlett Wilson called Roof's actions "the ultimate crime that deserved the ultimate punishment."
Prosecutors plan to present evidence on his mental state and his criminal records, as well as his alleged lack of remorse for the murders in June, reported The New York Times.
The 21-year-old has been charged by the state with nine counts of murder, three counts of attempted murder and the use of a firearm during a violent felony.
Roof indicated in federal court on July 31 that he intended to plead guilty, but his lawyers said he couldn’t make the plea without knowing whether it could bring on the death penalty.
On June 17, Roof walked into Emanuel African Methodist Episcopal Church and sat in a Bible study session for almost an hour before drawing a semi-automatic handgun and shooting.
His friends said he was obsessed with the Ferguson, Missouri riots and the Trayvon Martin case.
Joseph Meek Jr. told the Today show: "He was just saying how he didn't agree with the Trayvon Martin case and how he wanted segregation. How he wanted white be with white and black be with black."
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