The FBI arrested the leader of a violent California neo-Nazi gang on a federal conspiracy charge after he fled the country earlier this month.

Robert Rundo, 28, of Huntington Beach, California, is being held at the federal jail in downtown Los Angeles. He was charged in a criminal complaint that was unsealed Tuesday.

Rundo apparently crossed into Mexico two weeks ago from California and then made his way to Central America. He was later brought back to the United States, where he was arrested Sunday at Los Angeles International Airport, according to two people familiar with the case who spoke on the condition of anonymity because they was not authorized to speak publicly.

He is the founder of the Rise Above Movement, a neo-Nazi gang based in Southern California whose members were involved in violent activity at protests throughout California in 2017. He and three other Californians associated with the group — Robert Boman, 25, Tyler Laube, 22, and Aaron Eason, 38 — were charged with inciting riots, according to court documents. Boman and Laube were arrested Tuesday morning in Southern California. The FBI said it was still searching for Eason.

Earlier this month, another four members of the Rise Above Movement — Benjamin Daley, Michael Miselis, Thomas Gillen and Cole White — were indicted on conspiracy to riot charges for attacking counterprotesters during last year’s Unite The Right rally in Charlottesville, Virginia.

The FBI said that Rundo and others attacked protesters in 2017 in Huntington Beach; the University of California, Berkeley campus; San Bernardino, California; and Charlottesville. The criminal complaint outlined the group’s hateful ideology and its embrace of violence.

At a rally March 25, 2017, in Huntington Beach, Laube grabbed a journalist and punched him in the face three times, according to videos of the incident that the FBI referenced in the complaint. During the same rally, the FBI said, videos showed that Rundo punched one protester in the back of the head, then assaulted a second protester.

Later that same day, Daley, who was at the rally, sent a text message to another member of the group bragging about the incident: “Front page of the stormer we did it fam.” The stormer is a reference to “The Daily Stormer,” the neo-Nazi website.

In April 2017, Rundo and others traveled to Berkeley, California. Video referenced in the complaint showed the men taping their hands in preparation for fighting and wearing skeleton masks. Boman is also seen punching at least two people. Rundo later attacked another protester and then punched a Berkeley police officer twice in the head before he was subdued and arrested.

The FBI said Rundo and other gang members used the internet “to prepare to incite and participate in violence” at various political events and committed violent assaults while at those events. The FBI added that the men applauded each other for the attacks and “publicly documented their assaults in order to recruit more members” to carry out violence.

The FBI’s joint terrorism task force in Los Angeles led the investigation. Nicola T. Hanna, the top federal prosecutor in Los Angeles, said in a statement Wednesday, “Every American has a right to peacefully organize, march and protest in support of their beliefs — but no one has the right to violently assault their political opponents.”

Rundo appeared before a federal judge in Los Angeles on Tuesday morning and was ordered detained pending trial. Boman and Laube were also expected to make an initial appearance in federal court.

Before founding the Rise Above Movement, Rundo served 20 months in a New York state prison for stabbing a rival gang member from MS-13 in a 2009 attack in New York. At the time, he was part of a small, multiracial neighborhood gang called the Original Flushing Crew, which was in a feud with a subset of MS-13, known as the Guanacos Little Cycos Salvatruchas, according to a 2012 federal indictment.

Rundo’s ties to white supremacist groups and ideology have gradually deepened since his sentencing, according to the authorities. Since creating the Rise Above Movement sometime around 2017, Rundo has established ties between the group and the West Coast chapter of the Hammerskins, an international network of neo-Nazi skinheads whose members have been involved in at least nine murders in four states.

Earlier this year, Rundo traveled to Europe with members of the Rise Above Movement to participate in mixed-martial arts tournaments hosted by neo-Nazi organizations in Germany and Ukraine. While in Europe, the FBI said, Rundo and others celebrated Adolf Hitler’s birthday and met with members of European white supremacists.