A federal grand jury in South Carolina returned a 33-count indictment against Dylann Roof, accused of a deadly shooting spree during Bible study at a historic black church last month, Lynch said.
The federal government has not decided if it will seek the death penalty if Roof is convicted, she said.
South Carolina is one of the few U.S. states that does not have a hate crimes statute. So the charges in the federal hate crime that Roof targeted the victims "because of their race and in order to interfere with their exercise of religion" are part of the federal indictment, Lynch said.
"The parishioners had Bibles. Dylann Roof had his .45 caliber Glock pistol and eight magazines loaded with hollow point bullets," Lynch said.
She noted that Roof had singled out the nearly 200-year-old Emanuel African Methodist Episcopal Church because of its historical significance in the African-American community. She said he had been planning the attack for several months.
Roof, 21, has already been charged with nine counts of murder in state court in Charleston in the June 17 shooting. If found guilty, he could face the death penalty. He also faces three counts of attempted murder.
Following the massacre, a website linked to Roof surfaced containing a racist manifesto, showing him in photos posing with a Confederate flag, viewed by many as a symbol of racism.