Federal officials have previously said that the shootings generally meet the legal requirements for a hate crime and that federal charges were likely. Roof, who is white, appeared in photos waving Confederate flags, and survivors told police that he hurled racial insults during the attack.
After the attack, an apparent manifesto of Roof's popped up online. In it, he appears to write about his alleged plot, including why he picked Charleston as the site for the attack: "I have no choice. I am not in the position to, alone, go into the ghetto and fight. I chose Charleston because it is most historic city in my state, and at one time had the highest ratio of blacks to Whites in the country."
A law enforcement source told CBS News' Pat Milton that eye witness told authorities that Roof stood up in the church and said words to the effect that he was there to shoot black people, and then uttered other derogatory remarks.
A law enforcement source told CBS News that at the time of the shooting, Roof was essentially homeless. He had no fixed address, and moved from place to place. The FBI is interviewing his parents.
A friend says Roof had told him recently that black people were taking over the world and that something needed to be done for the white race.
Roof already faces state charges including nine counts of murder. State prosecutors have not said whether they'll seek the death penalty.