One of four California men accused of violently attacking counterprotesters at the deadly "Unite the Right" rally in Charlottesville has pleaded guilty to conspiracy to riot.

Thomas Walter Gillen, 25, a member of the Rise Above Movement, a white supremacist group, entered the guilty plea on Monday in U.S. District Court, where he admitted traveling to rallies in California and Virginia with the purpose of committing acts of violence.

Four members of the group

. In addition to Gillen, the other three were Benjamin Drake Daley, Michael Paul Miselis, and Cole Evan White.

In November, White

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Miselis and Daley, who prosecutors say both traveled to Europe after the Charlottesville rally to meet with neo-Nazi and fascist groups and attended a festival in Germany celebrating Adolf Hitler's birthday, are

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Their lawyers attempted to have their case dropped by arguing that their actions were protected by the First Amendment, but that bid was unsuccessful.

“The First Amendment protects an individual’s or organization’s right to speak, assemble, and espouse political views, but it does not license insensate acts of violence committed under the guise of First Amendment expression,” U.S. Attorney Cullen stated. “As Mr. Gillen has admitted as part of his guilty plea, he and other members of RAM attended the Unite the Right rally and other purported political demonstrations in California to incite and commit acts of violence, not to exercise their rights to free speech. We are grateful for the commitment of the FBI and the Virginia State Police in bringing these defendants to justice.”

According to plea documents, Gillen was part of the Rise Above Movement, a California-based militant group that represents itself as a white supremacist movement.

According to The Anti-Defamation League, Rise Above Movement members believe they are fighting against a "modern world" corrupted by the "destructive cultural influences" of liberals, Jews, Muslims and non-white immigrants. Members refer to themselves as the mixed martial arts club of the "alt-right" fringe movement, a loose mix of neo-Nazis, white nationalists and other far-right extremists.

"They very much operate like a street-fighting club," said Oren Segal, director of the ADL's Center on Extremism.

Members of the group frequently posted photos and videos of themselves training in mixed martial arts and street fighting techniques, along with anti-Semitic and white supremacist propaganda.

Prosecutors say they also expressed and promoted violence against those they perceived as enemies.

From about March 2017 to August 2017, members of the group traveled to a variety of rallies in California and the Charlottesville rally, where they engaged in acts of violence.

Documents show they pursued and assaulted protesters in Huntington Beach on March 25, 2017, and later celebrated news coverage of the assaults, using photos and video of the assaults to recruit more members.

The next month, on April 15, Gillen and other RAM members followed and attacked a group of protesters in Berkeley, California. Gillen acknowledged punching one protester several times and stomping on him, which was caught on video and posted to YouTube.

Gillen sent the video to a friend after the rally, writing “20 seconds in I’m in the grey shirt turning up a commie.”

The RAM Instagram account posted a photograph of a RAM member wearing a black skull mask at the Berkeley event along with the comment, “#rightwingdeathsquad.”

Then, a few months later, Gillen, Daley, Miselis, and Cole planned to travel across the country to Charlottesville for the "Unite the Right" rally. Gillen bought a one-way ticket from American Airlines leaving on August 11.

He planned to engage in violent confrontations in Charlottesville.

Upon arrival, documents show RAM members, including Gillen, purchased athletic tape at Wal-Mart to wrap their wrists to prevent their hands from breaking when they engaged in street violence.

On the evening of August 11, prior to the scheduled rally, Gillen and other RAM members were among the torch-lit march on the grounds of the University of Virginia, where chants of “Blood and soil!” and “Jews will not replace us!” erupted before the march culminated near a state of Thomas Jefferson, where the white supremacists encountered a group of student protesters.

Punching, kicking, spraying of chemical irritants, and swinging torches ensued. Gillen struck multiple people with a torch, and court documents indicate it was not in self-defense.

The following morning, Gillen and the other RAM members, with their hands wrapped in athletic tape, were part of a group of about 40 people trying to get into Emancipation Park from Second Street when law enforcement told them that way was blocked.

The group turned around, lined up, and began to make their way through a group of about 20 people who came to the rally to protest discrimination. As they made their way through, Gillen and the other RAM members collectively pushed, punched, kicked, choked, head-butted, and otherwise assaulted a number of people, resulting in a riot.

Gillen faces a maximum statutory penalty of five years in prison and a $250,000 fine at sentencing, which has not been scheduled yet.