Dylann Roof has been found guilty on all 33 counts in the federal trial in connection with the June 2015 shooting at a Charleston, South Carolina, church.
He showed no emotion as the verdict was read.
Roof, who is white, was accused of fatally shooting nine black parishioners during a Bible study at the predominantly black Emanuel AME Church on June 17, 2015. According to the federal indictment against him, Roof, 22, entered the church armed and "with the intent of killing African-Americans engaged in the exercise of their religious beliefs."
The 33 federal counts against Roof included hate crimes resulting in death and obstruction of exercise of religion resulting in death.
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The trial next moves into the sentencing phase, in which the same jury will determine whether or not Roof will be sentenced to death or life in prison. That will begin on Jan. 3.
After the reading of the verdict, the judge explained to Roof the gravity of the sentencing phase, asking him whether he wants to reconsider representing himself during this phase.
Roof told the judge that he understood and that he plans to self-represent in the sentencing phase. The judge said that he will give Roof until Jan. 3 to reconsider, but once the sentencing phase begins, the decision to represent himself holds.
Roof mocked during closing arguments
In closing arguments, Assistant U.S. Attorney Nathan Williams mocked Roof for calling himself brave in his hate-filled journal and during his confession, saying the real bravery came from the victims who tried to stop him as he fired 77 bullets at Emanuel African Methodist Episcopal church.
"Those people couldn't see the hatred in his heart any more than they could see the .45-caliber handgun and the eight magazines concealed around his waist," Williams said.
Defense lawyer David Bruck conceded Roof committed the slayings, but he asked jurors to look into his head and see what caused him to become so full of hatred, calling him a suicidal loner who never grasped the gravity of what he did.
The defense put up no witnesses during the seven-day trial. They tried to present evidence about his mental state, but the judge ruled that it did not have anything to do with Roof's guilt or innocence.
Roof was just imitating what he saw on the internet and believed he had to give his life to "a fight to the death between white people and black people that only he" could see and act on, Bruck said.
Williams' 50-minute closing argument filled the court with tension. At times, the prosecutor raised his voice, saying Roof was a cold, calculated killer. Some family members of victims dabbed their eyes with tissues, and jurors appeared emotional when Williams, after apologizing to them, showed crime scene photos of each person killed alongside a small picture of them while alive.
Those pictures included the Rev. Clementa Pinckney, 41, Emanuel AME's pastor and a state senator; Myra Thompson, 59, who taught Bible study that night — the same night she was licensed to preach; Cynthia Hurd, 54, a librarian who stayed to support Thompson; Depayne Middleton-Doctor, 49, who friends said sang like an angel and was also license to preach the day of the shootings; Daniel "Dapper Dan" Simmons, 74, nicknamed for his shiny shoes and fine hats; Sharonda Coleman-Singleton, 45, a high school track coach heavily involved in the church's youth programs; Ethel Lance, 70, the church sexton who kept the bathrooms and building immaculately clean; Susie Jackson, 87, who sang in the choir and sent generations through the church; and Tywanza Sanders, 26, Jackson's nephew and an aspiring poet who wanted to work with children.
The prosecutor said the good of all those faithful churchgoers prevailed over Roof's hatred.
"This defendant chose to take their lives. He chose to break their bodies. But he does not get to choose who they were," Williams said.
Gov. Nikki Haley releases statement following verdict
In a statement, South Carolina Gov. Nikki Haley said, "It is my hope that the survivors, the families, and the people of South Carolina can find some peace in the fact that justice has been served."
Haley threw her support behind removing the Confederate flag from the grounds of the South Carolina Statehouse after Roof was seen posing with the rebel banner. She spent her first four years in office calling it a settled issue.
Haley also went to the funerals of all nine victims and has stayed in touch with their families.
Roof also faces a state trial, set for early next year, in which he may also face the death penalty.
Information from ABC News was used in this report.