Debate is raging over whether those who caused chaos at the Milo Yiannopoulos protests were from the left or the right.

In the six days since rioters hijacked a raucous, but peaceful protest against the right-wing speaker Milo Yiannopoulos, many have wondered who those masked marauders actually were. The 100 to 150 people who stormed Sproul Plaza and who UC officials said hurled fireworks, rocks, and Molotov cocktails at police were mostly dressed in black with ski masks or bandanas hiding their faces.

Were the troublemakers from the left? Or from the right?

Now the Federal Bureau of Investigation has been called in to help figure it out.

Immediately after the protests, which caused $100,000 in damage to the MLK student union, the Amazon store on its first floor, and at least one tree, UC Berkeley officials described the rioters as acting as a coordinated paramilitary force that had “essentially raided the campus.” There were similarities among the rioters that this reporter noticed; many of them carried the same rounded long sticks that they used to hold up flags or, perhaps, to smash windows.

“They came in a military fashion, they were well-rehearsed,” said UC Berkeley spokesman Dan Mogulof on the night of the protests. “They seemed armed and dangerous.”

About 1,500 people were peacefully protesting against Yiannopoulos’s scheduled talk in the plaza when the group of black-clad protesters rushed onto campus en masse around 5:50 p.m. Within a few minutes, they had moved the metal barricades set up to create a space for those attending the talk to pass through, and had thrown several of the barriers through ground-floor windows. They also set a generator on fire, providing the dramatic images of the protest that have been flashed around the world. The black-clad protesters then occupied the area nearest the student union for most of the night while others stood on the steps of Sproul Hall or gathered further away.

Later in the night, the agitators rampaged through downtown Berkeley, damaging numerous banks, a Starbucks, and branches of other national chains. John Caner, head of the Downtown Berkeley Association, said there was an estimated $400,000-$500,000 worth of damage to downtown. There was also some vandalism on Telegraph Avenue, including graffiti, according to Stuart Baker, head of the Telegraph Business Improvement District, but it was relatively minor.

UC Berkeley Professor Robert Reich speculated on his website that right-wing agitators might have been behind the rioting. He wrote of the “possibility that Yiannopoulos and Breitbart were in cahoots with the agitators, in order to lay the groundwork for a Trump crackdown on universities and their federal funding.”

CNN interviewed Reich on Friday where he said he “wouldn’t bet against” the possibility that the chaos was deliberately planned by the right. But Reich did not provide any direct evidence of his assertion.

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A Berkeleyside reader also brought up the possibility that those on the right were to blame.

“It’s a well-known fact that the far right infiltrates social justice movements and events in the hopes of distorting the media’s and the public response to the event,” she wrote. “I would not be at all surprised if those who came from off-campus (probably from outside the city) were supporters of Milos Yiannopoulos. Whether they came on his behalf or another source, I imagine they are very satisfied with their accomplishment; they had the media (local and national) pretty much eating out of their hands, as far as I can tell.”

However, much of the media covering the event described the rioters as anarchists or “black bloc,” or “antifa” — loose collections of people on the far left who believe creating chaos is the best way to trigger social change. Members of the black bloc have been popping up at protests for several years, ever since the Occupy movement took root.

At least one far-left group has publicly acknowledged its participation in the protest, although it has not said it caused property damage. The group, By Any Means Necessary (BAMN), a left-wing group that is often confrontational, has claimed that it was one of the “organizers of Berkeley’s shutdown of white neo-fascist Milo Yiannopoulos.” One of its leaders, Yvette Felarca, who is also a BUSD middle-school teacher, spoke against Yiannopoulos through a megaphone at the protests, and later told Berkeleyside the chaos and destruction were a “stunning achievement.” However, BAMN members, including Felarca, were not dressed in the black “uniform” of the most destructive members of the crowd.

People who identify as conservatives and Trump supporters have spent considerable energy on social media and in Berkeleyside’s comments section discussing the possible identities of the rioters and who may be funding them. The #Berkeley hashtag on Twitter is clogged with claims and accusations about who caused the destruction. Many argue that the demonstrators were Cal students and that this proves the Free Speech Movement has died. They blame students and the university administration for canceling Yiannopoulos’ talk. They are also highly critical of the police’s decision to not engage with the protesters but to defend the MLK building from inside instead. (Read our interviews with both the UCPD chief and the BPD chief on their responses to the protesters.)

Some believe one of those who hit protesters works at UC Berkeley. They have identified him by name on Twitter and online. Breitbart News has listed his name, his Twitter handle and a screenshot of the salary he earns at Cal. As he has not been charged, Berkeleyside is not publishing his name.

Mogulof said UC Police are aware that some have claimed a UC employee was involved and are investigating the charge. He also said the federal government is now assisting with the investigation.

“The campus is aware of the allegations involving someone who is a current member of the university’s workforce,” Mogulof wrote in an email. “UCPD is working in close concert with the FBI on an ongoing investigation into the matter.”

The FBI on Wednesday responded to an email from Berkeleyside requesting information. It confirmed it was in contact with both the Berkeley police and UCPD, but would not confirm or deny an ongoing investigation about the violence that erupted at the protests. The FBI’s Prentice Danneriii also noted, by email, that the FBI does “not open investigations based on First Amendment activities.”

In an unusual twist, a woman who was pepper-sprayed while she was giving an interview is trying to find out the identity of the people she thinks attacked her. The woman, Katrina, identifies herself on Twitter as on the right end of the political spectrum. She was at Cal with her husband and friends to hear Yiannopoulos. She and a female friend were pepper-sprayed and her husband was hit so badly several of his ribs were broken and he had to go to the hospital, she said in an interview with radio host Stefan Molyneux.

Katrina is trying to find those who attacked her group by crowd-funding a bounty for information leading to their identification. She used a website to ask people to contribute to a fund (the bounty) to track her alleged attackers down. So far, people have contributed $1,272 to locate one of the alleged assailants, and $830 and $500 to find two others. If someone provides the correct information, they will get the money.

“Expose this pepper-spraying Antifa Ninja who assaulted an innocent woman,” reads one of the entries on the site. It continues on another page: “This criminal, caught red-handed on tape, must be identified, exposed, and turned over to law enforcement and the legal system so that justice can be served.”

Editors’ note: 1) This article originally had links to the crowd-funded bounty site. We took down the link after a phone call from someone who said it was putting her in danger. 2) This story was updated after publication with information received from the FBI.

Frances Dinkelspiel is co-founder and executive editor of Berkeleyside.