The decision comes less than a month before the first anniversary of the attack, which unfolded inside the historic Charleston church that birthed a slave rebellion and helped incubate the civil rights movement in that city.
Steve Schmutz, a lawyer representing family members of three victims, said federal officials held a conference call to inform relatives of the decision. Schmutz said he believed these relatives supported Lynch's decision.
"Regardless of whether or not you're for the death penalty, the thought process is this: where else would you have it, if not for here?" Schmutz said.
Roof was indicted on indicted on federal hate crime charges last northern summer, some of which were eligible for the death penalty, but the Justice Department spent months considering whether to seek a death sentence, causing the federal trial to be delayed multiple times.
State prosecutors had already announced their plans to seek the death penalty for Roof, who has been charged with nine counts of murder and three counts of attempted murder for the shooting spree. The state trial has also been pushed back after Roof's lawyers said they needed more time for him to undergo a psychiatric evaluation.
In the aftermath of the church shooting, authorities said they found a racist manifesto Roof had posted on his website and modified just hours before the rampage. This site was filled with racial stereotypes and diatribes against black, Jewish and Hispanic people as well as photos of Roof holding a .45-calibre Glock pistol and a Confederate flag.
Arthur Hurd, whose wife - 55-year-old Cynthia Hurd - was among the victims, said he thought seeking the death penalty was a "good idea" given the motivation Roof had expressed.
"Since he feels that strongly, then let the law of the land take care of it," Hurd said.
Hurd said Cynthia, a branch manager at a library, "went out of her way and helped everybody that she can." Today, after learning of the government's decision, Hurd said seeing Roof executed would not bring him any closure. Only a face-to-face conversation with Roof might do that, Hurd said. "Maybe I can get the feeling that, 'Hey, what in the world were you thinking about?'" he said.
Still, he offered one other thing that he said could help him. "I told them what would really bring me to a point of happiness would be that I was the one that pushed the plunger if he got injected," Hurd said.
Last month, Joey Meek - a friend with whom Roof stayed in the weeks before the rampage - pleaded guilty to charges of lying to the FBI and concealing his knowledge of the crimes. Meek had told the Post that before the church shooting, Roof had spoken of going to the church and doing "something crazy".
David Bruck, a lawyer for Roof, had said he would plead guilty to the federal hate crime charges, but also said he could not advise him until federal authorities decided on the death penalty. The judge then entered a "not guilty" plea for Roof at a hearing last summer, essentially a temporary plea until the death penalty decision could be made.
Bruck did not immediately respond to messages seeking comment.
It was unclear how the death penalty decision could have an impact on Roof's ultimate plea. A plea can ultimately be used as a way to avoid a death penalty in capital cases.
In perhaps the most famous example, Theodore Kaczynski - known as the Unabomber - ultimately struck a deal and pleaded guilty the day opening arguments were going to begin in his trial, reversing his longstanding stance of pleading not guilty. As a result, he agreed to a sentence of life in prison without possibility of parole and evading the death penalty.
While the federal Government has decided to seek this sentence, it cannot execute anyone right now. The Justice Department effectively has a moratorium on executions while it reviews the federal death penalty statute, and federal officials have said that the Bureau of Prisons does not possess doses of drugs needed for lethal injections due to the ongoing review.
Federal death sentences are rare, and executions under this statute are even rarer. Since the federal death penalty statute was reinstated in 1988 and expanded in 1994, the federal government has put three inmates to death.