Billy Roper and his white supremacist group Shield Wall Network interrupted a Holocaust Remembrance Day event in Russellville, Arkansas, this weekend with a small group of demonstrators who shouted anti-Semitic phrases and carried Nazi flags.

Arkansas outlet KFSM 5News reported that members of Shield Wall Network interrupted a Holocaust Remembrance Day event in Russellville on May 5, 2019. Roper told 5News that their demonstration was in support of deceased Arkansas Tech University professor Dr. Michael Link, who Jewish rights groups say promoted anti-Semitic worldviews and Holocaust denial. The groups voiced their concerns in a letter sent to university officials, objecting to a scholarship established in Link’s name and funded by his estate.

“First, Dr. Link presented misinformation as history. Second, he presented the anti-Semitic nature of this misinformation as though it were truthful, correct and acceptable. Third, he presented the question of whether the Holocaust occurred—an irrefutable historical fact—as though it were an appropriate, valid point of debate,” read the letter sent to Arkansas Tech University protesting the scholarship fund.

In footage from the event, Shield Wall Network members can be heard chanting “six million more,” which is a reference to the six million Jews murdered during the Holocaust. Members of Shield Wall Network heckled a World War II veteran and Arkansas Tech University professor as they spoke at the event and the group roamed the streets of downtown Russellville behind a police line.

Roper is an Arkansas-based activist recognized by the Southern Poverty Law Center as a neo-Nazi. SPLC reports that Roper was born into a family of Klansmen and joined a “racist skinhead gang in Arkansas as a teenager” before organizing his own hate groups. Roper joined state chapters of the neo-Nazi group National Alliance in the 1990s, and the white supremacist group Council of Conservative Citizens. Currently, Roper leads the Shield Wall Network out of Arkansas, which has an explicit goal “to build a white ethno-state,” the Anti-Defamation League reports.

On behalf of the anti-Muslim group ACT! For America, which has bragged about its relationship with the Trump White House, Roper organized a “March Against Sharia” in Arkansas in 2017. The group then disavowed Roper. Shield Wall Network has collaborated with neo-Confederate groups in the region for recent rallies.