A grand jury indicted the 21-year-old on 33 charges including hate crimes, firearms violations and obstructing the practice of religion after determining that the man allegedly targeted his victims on the basis of their race and religion, according to the Associated Press.
U.S. Attorney General Loretta Lynch said during a news conference on Wednesday that Roof sought out African Americans and "racially motivated violence such as this is the original domestic terrorism."
Lynch said Roof, who has reportedly admitted to the killings, planned the attack for months and took advantage of his alleged victims' hospitality after they welcomed him into their weekly Bible-study session.
"The parishioners had Bibles. Dylann Roof had his .45-caliber Glock pistol and eight magazines loaded with hollow-point bullets," she said.
Roof could face life imprisonment or the death penalty. However, Lynch said, the Justice Department has not decided whether it will seek the death penalty.
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Roof also faces state charges of murder and attempted murder in the June 17 shooting.
His state trial is tentatively scheduled to begin in July 2016, per NBC News.
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