Dylann Roof, accused of a mass shooting that killed nine black church members in Charleston, S.C., last month, was indicted Wednesday on 33 federal counts, including hate crimes, firearms violations and obstructing the practice of religion. The latter could carry the death penalty.

What does it mean that Roof will face hate crime charges, and not charges related to domestic terrorism? (He already faces nine murder charges at the state level.)

The federal government is now seeking to prove that race was a primary factor in the crimes — something, officials said, that was compelled by the shooting's "horrific" nature. And the federal government has to bring these charges itself: South Carolina, like Georgia and three other states, does not have hate crime legislation.

But successfully building a case for them can be "challenging," acccording to the Associated Press, because the government "must prove that a defendant was primarily motivated by a victim's race or religion as opposed to other factors" such as drug addiction or mental illness.

Roof was allegedly in contact with white supremacist groups before the shooting, was pictured with racist symbols and allegedly authored an Internet manifesto exclaming, in part, "I chose Charleston because it is [the] most historic city in my state, and at one time had the highest ratio of blacks to Whites in the country."

"You are raping our women and taking over our country," Roof said in the church as he fired on the victims, witnesses later said.

But it's not clear what legal effects such charges will now have; and, according to the Times, the Justice Department could delay its own prosecution until after Roof's murder trial, which is tentatively scheduled for July 11, 2016.

In announcing the indictment Wednesday, U.S. Attorney General Loretta Lynch called "racially-motivated violence such as this is the original domesticated terrorism.” She said that "no decision has been made" about whether to seek the death penalty.

But she did not announce that Roof would face charges related to domestic terrorism, though the Justice Department has previously said it was "looking at this crime from all angles, including as a hate crime and as an act of domestic terrorism." This view was echoed by former U.S. Attorney General Eric Holder.

The FBI is the final arbiter of the issue, one professor told New York Magazine: "If the FBI labels it as terrorism, it is terrorism. If they don't, it isn't."

Earlier this month, FBI Director James Comey said he wasn't yet sure if it was.

"Given the nature of my business, I only operate in a legal framework," he said. "... So I'm not hesitating to define it in any way, except to say that that we want to gather the facts and then find out which statutes make sense. That would be the same whether his manifesto was written in Arabic or in English."