Note: This story has been updated as new information became available. See the critical updates at the bottom of this post.

Last week, Correct The Record (CTR), David Brock’s super PAC that coordinates with Hillary Clinton’s presidential campaign, announced that it was spending $1m on social media in an effort to combat Bernie Sanders’ online dominance. How, specifically? By paying trolls.

Last night, on the eve of five Democratic Primary elections—Connecticut, Rhode Island, Delaware, Pennsylvania, and Maryland—we may have seen this paid army in action. Several notable Bernie Sanders Facebook groups were taken down following a coordinated cyber attack by Clinton supporters, in which a number of users reported content on the pages simultaneously. According to US Uncut, “Facebook’s automated systems take note of how many individuals report a particular post, and if the post is reported enough, it will be taken down. This same process applies to groups, pages, and individual user accounts.”

The groups affected by the attack include (but are not limited to) the following:

Bernie Sanders Activists (40,122 members)

Bernie Sanders Is My Hero (60,097 members)

Bernie or Bust (16,812 members)

Bernie Sanders – Ideas Welcome (33,836 members)

Bernie Sanders for President 2016 (117,601 members)

Bernie Sanders Revolutionaries

Bay Area for Bernie

Thus far, there is limited evidence for which group or groups were behind these attacks, and we’ll update this page as more information comes in (see the bottom of this post for current updates). The Facebook purge didn’t last long—perhaps long enough to prevent the spread of anti-Clinton information in key hours of the evening before the primaries—but it coincided with the ThingsBernieHates hashtag (#ThingsBernieHates) trending on Twitter, which was quickly co-opted by Bernie’s grassroots online movement.

Needless to say, Sanders supporters were outraged. The Reddit group /r/SandersForPresident/ became a central hub during the down time. There and elsewhere, many angry users exchanged theories that this was the work of CTR’s paid trolls who had spammed the groups, posting inappropriate pornographic materials, only to then report the material to Facebook.

According to US Uncut, there were even allegations of child porn being circulated and posted by the Clinton trolls:

Erica Libenow, a Sanders supporter and member of one of the pro-Bernie groups, said, “We had what looked like a kiddie porn posted in one of our groups today. I reported that one. Seriously made me want to vomit.”

A Facebook post by “Casey Champagne”, whose secondary name on his profile was listed as “Casey Max Charbonneau” (pictured below with Hillary Clinton) and whose Facebook likes included Correct The Record and Barrier Breakers 2016 (Brock’s recently launched online operation), confirmed that Clinton trolls were behind the attack when he bragged in the Facebook group “Bros 4 Hillary” that he managed to get one of the groups banned for “containing credible threat of violence”:

That user’s profile has since been deleted, but the comments on his post seem to confirm that this tactic is nothing new for Clinton’s online supporters:

It should be noted that there is nothing officially linking Brock’s Barrier Breakers to the Facebook attacks, and beyond the post on Bros4Hillary (which has itself been shut down in response), there’s no clear evidence who was behind the coordinated attacks.

But let’s say, for argument’s sake, that this purge was a move by David Brock to silence Hillary Clinton’s online opposition during the crucial evening hours before five primary contests, and prevent a contested convention. Let’s also say it was calculated to generate disproportionate backlash to feed the narrative that Bernie’s online supporters are bullies and aggressive. Does this really make sense?

Such a tactic would be unlikely to win the hearts of any Sanders supporters who Hillary Clinton will need in a general election. Even the perception among Bernie’s progressives that this was a plot by Brock will, in all probability, push many into the growing ‘Bernie Or Bust’ Movement. These fed up voters now represent a large enough slice of the Democratic base to cost Clinton victory in a close race.

And 2016 promises to be close. Clinton, whose favorability ratings continue to tank, is only up on average by 8.5 points over Republican front-runner Donald Trump, according to RealClearPolitics. A recent poll saw that number shrink to three. Hillary Clinton’s camp might not feel it needs Bernie’s progressives, but it absolutely does.

Though there is plenty of circumstantial evidence, logically speaking, the negatives of this scenario seem to outweigh the benefits.

That said, even if last night had nothing to do with David Brock, Correct The Record, or Hillary Clinton’s campaign, it was still supporters of the former Secretary of State who carried out the assault. Such an affront to the free sharing of information on the internet is indicative of an increasingly hostile Clinton camp that has, for too long, gotten a pass by a mainstream media fixated on “Bernie Bros.” This incident marks the first time in this Democratic primary where these tactics have been used, and puts the lie to the idea that the dirtiest players online are Sanders supporters. In fact, it is the single largest online attack by supporters of one Democratic candidate against supporters of the other in 2016.

If she wants to have any chance in November should she secure the nomination, Hillary Clinton should at least consider denouncing these strategies, and should do everything to rein in her most extreme supporters, who are doing her no favors by carrying out a war with Sanders supporters online at a time when the primary race has all but been decided. Further, the precedent this sets should frighten everyone who values free speech in America. And if it turns out that Brock really is behind the attack, Clinton should promptly abandon him as an ally—in fact, she should do that anyway. These tactics have no place on the left.

UPDATE 1: Bros4Hillary issued a statement disavowing Casey Charbonneau, while Correct the Record has denied any involvement.

UPDATE 2: Facebook issued a statement saying that “a number of groups were inaccessible for a brief period after one of our automated policies was applied incorrectly.” The Daily Beast claims, citing a Facebook source, that thousands of groups were affected. There are no specifics about what exactly those bots were responding to. We’ve reached out to Facebook, and will update again when and if they respond.

UPDATE 3: A Facebook spokesman told us that they weren’t clear on the exact technical details of what transpired to take the Sanders groups down, and that they couldn’t discount that the disabling of the groups may have been triggered by a higher volume of users reporting inappropriate content.