When he learned Don Gathers, a Black Lives Matter activist in Charlottesville, planned to run for a seat on the city council last year, a Florida man who called himself “the antifa hunter” organized a racist social media campaign that eventually led Gathers to quit the race over fears for his safety.

In a hearing over video conference on Monday, Gathers told the man that he hopes one day he might be able to forgive him for his actions, the Associated Press reported.

“But today is not that day,” Gathers said. “I despise all that you and others like you represent.”

Daniel McMahon, 32, of Brandon, Fla., was sentenced Monday to three years and five months in federal prison for cyberstalking and bias-motivated intimidation and interference with a candidate for elected office. McMahon pleaded guilty in April to attacking Gathers online and to threatening to sexually assault the daughter of another activist who protested white supremacists.

“This defendant weaponized social media to threaten and intimidate his perceived political enemies and propagate a violent white-supremacist ideology,” said U.S. Attorney Thomas T. Cullen of the Western District of Virginia in a news release. “Because his online activity crossed the boundary between protected First Amendment expression and unlawful threats and harassment, he will spend considerable time in federal prison.”

McMahon’s case played out against national concerns about the rising threat of violent far-right groups, and his sentencing came shortly after deadly clashes between racial justice protesters and armed, self-described militia members in Oregon and Wisconsin.

McMahon began targeting Gathers, 61, in January 2019 after the co-founder of Charlottesville’s Black Lives Matter chapter announced his intent to run for public office. Gathers had also served on a committee dedicated to relocating Confederate statues in the wake of the deadly white supremacist Charlottesville Unite the Right rally in 2017.

McMahon, using the pseudonym Jack Corbin, began posting threats on Gab, a social media website popular with far-right users. He used racist slurs, called Gathers a “terrorist” and warned him not to run for office. McMahon also said he’d use “a diversity of tactics” to stop his candidacy, a phrase known by white supremacists as a euphemism for violence, according to court documents.

Before his campaign kickoff event on Jan. 8, 2019, the FBI notified Gathers of McMahon’s threats, the AP reported. The FBI had been tracking McMahon’s activities online under several pseudonyms, since an investigation into white supremacist activity at the Unite the Right rally.

Gathers ultimately decided not to run. Upon learning the news, McMahon posted “Hail victory!” on Gab.

The FBI arrested McMahon in September 2019, charging him with forcing Gathers out of the race. Soon after his arrest, a woman contacted federal agents to report that McMahon had also been cyberstalking her and threatening to sexually assault her underage daughter, who has autism.

The woman, who wasn’t identified in court documents, regularly protested against white nationalist and pro-Confederate groups. McMahon harassed her on Facebook, using one of his pseudonym accounts called “Restore Silent Sam,” a reference to a Confederate statue at the University of North Carolina.

In a stream of disturbing messages, McMahon detailed how he would sexually assault her daughter and accused the woman of being in antifa. “You failed your daughter,” he wrote. “You chose antifa, a terrorist group, over your own daughter.”

McMahon also posted the daughter’s image on a racist social media platform and Googled terms like “sex with autistic girls,” court documents said.

“Only a deeply disturbed individual would do this, a monster,” the woman wrote in a statement that was read by a court employee at McMahon’s sentencing hearing on Monday, the AP reported. “I will never feel completely safe about my child again.”

“There is seemingly nothing that Daniel McMahon will not do in the name of white supremacy,” she wrote.

McMahon also methodically kept track of his white supremacist activities, prosecutors noted. He had 278 folders with the word “owned” in the title, signifying people he had harassed online. Other folders contained personal information about targets, including images of their children. He also kept graphic images of Trayvon Martin, a Black teenager who was fatally shot in Florida in 2012, prosecutors said.

McMahon’s sentencing also includes three years of supervised release following his time in prison. McMahon’s attorney had no comment.

“Americans have the right to run for office in this country without facing racially-bigoted threats of violence,” said Assistant Attorney General Eric Dreiband for the civil rights division of the Department of Justice in a news release. “Furthermore, no American should have to live with hateful threats of sexual violence for opposing white nationalism."

During his remarks at the sentencing on Monday, Gathers told McMahon that white supremacists would be defeated.

“A new day, a different day, is coming,” Gathers said, according to the AP. “Like it or not, Black lives matter."