The white supremacist who organised the Charlottesville rally called counter-protester Heather Heyer a "fat, disgusting communist" and described her death as "payback" in a tweet he later blamed on "xanax, ambien and booze".
Jason Kessler, 34, gloated over the 32-year-old's alleged murder on social media after she was run over and killed in a shocking attack at the "Unite The Right" event in Virginia on 12 August.
Mr Kessler, who blamed "anti-white hate" for violent clashes between protesters, tweeted: "Heather Heyer was a fat, disgusting Communist. Communists have killed 94 million. Looks like it was payback time."
The offensive post also contained a link to a defamatory story about Ms Heyer on the neo-Nazi website The Daily Stormer.
Mr Kessler initially claimed his Twitter account had been hacked after seeing the angry backlash from people across the political spectrum on Friday night, writing: "I was hacked last night. I apologize for the tweet sent out from my account last night."
But the following day, a post on the far-right activist's account appeared to admit he wrote the words, before blaming it on a mixture of alcohol and prescription drugs.
"I sometimes wake up having done strange things I don't remember," he explained, before apologising again for his "heinous" comments.
His remarks sparked outrage and were even condemned by fellow white supremacists including National Policy Institute president Richard Spencer.
"I will no longer associate w/ Jason Kessler; no one should. Heyer's death was deeply saddening. "Payback" is a morally reprehensible idea," tweeted Mr Spencer.
Mr Kessler has since deleted his account and says he has been forced into hiding due to "a crushing amount of stress and death threats" in the wake of the Charlottesville rally.
Hundreds of Ku Klux Klan members and neo-Nazis attended the event he organised to protest against a vote by the city’s government to remove a statue of a Confederate general, Robert E Lee, from a local park.
The day was marred by violence which turned deadly when far-right activist James Fields Jr allegedly rammed his Dodge Challenger into a crowd of counter-protesters, killing Ms Heyer and leaving 19 others injured.
Mr Kessler, president of grassroots organisation Unity and Security for America, was unapologetic during a press conference a day after the tragic events.
He told a jeering crowd: “The hate that you hear around you? That is the anti-white hate that fuelled what happened yesterday. What happened yesterday was the result of Charlottesville police officers refusing to do their job.”
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