A little over a week ago, a group of people marched down the streets of Manhattan and called for police to be killed. But exactly who cried out for violence has been something of a mystery as New York goes through its most tense moment in more than a decade.

Evidence from photos, videos, social-media posts and interviews suggest that a group—the New York chapter of the Trayvon Martin Organizing Committee, or TMOC—might have been involved. There is no definitive proof that TMOC led the call for dead cops, but there is a web of circumstantial ties with the group at its center.

TMOC’s own social-media posts put them near the scene of the cry for police blood. Some of the slogans used that night—including “arms up, shoot back!”—are the same as the ones used by TMOC. And recently TMOC has been soliciting money for the legal defense of people it calls its “comrades” who were arrested for allegedly assaulting police officers on the Brooklyn Bridge, just hours after the “dead cops” chant was recorded.

The bedrock of TMOC’s politics, judged by their social-media output, is hatred for police and endorsement of violence against them. The group seems to blend “black bloc” anarchist street violence with social-media campaigns. Keeping their organizing online, members can plan and incite without coming out from behind their digital masks until they hit the streets. (The group did not respond to repeated requests for comment.)

Finding TMOC started with an interview of the man who shot the video showing marchers chanting, “What do we want? Dead cops! When do we want it? Now!”

It’s impossible to make out any faces in the video, which was shot from a roof at night. The person who took the footage didn’t know anything about the people involved. He told me that all he could see was the banner carried at the front of the group which read, “No Cops No Prisons.”

An Instagram of that “No Cops No Prisons” banner displays a number of hashtags, including #turnuptheanger, a hashtag associated with TMOC. (The first mention of #turnuptheanger on Twitter, for example, directs to a Facebook page hosted by the Trayvon Martin Organizing Committee NYC.)

It’s not the only apparent link between the “dead cops” chant and TMOC. At the beginning of the video and before the call to kill police, you can hear what sounds like, “arms up, shoot back!” That slogan appears on TMOC’s Twitter account.

The day before the December 13th, Millions March, a nationwide protest concerned with racial justice and policing, TMOC began planning a march within the march using “Turn up the anger” as their rallying cry. The hashtag also served another purpose. People using it effectively opened a secret channel on an a public platform. Anyone who typed #turnuptheanger into Twitter could post photos or write messages only seen by others who knew the hashtag.

Facebook’s digital flyer for “turn up the anger” has 1,900 invites, 356 people reporting they attended and 44 listed as maybes. A small group but one whose insurgent mentality, targeting peaceful protesters along with police, gave it an outsize impact.

Ashoka Jegroo is a freelance reporter and graduate of the City University of New York’s journalism school. He has been attending the protests in New York and documented the #turnuptheanger contingent of the Millions March.

By email he told me, “the #turnuptheanger hashtag was just used by the more radical wing of the movement that day.” Jegroo said he has “no idea” who started the #turnuptheanger hashtag but knew of the Trayvon Martin Organizing Committee, which he has seen at past protests. TMOC is “just one of many groups—but definitely one of the more radical groups—in this movement who organize actions,” Jegroo said.

“I saw the ‘dead cops’ chant on YouTube,” Jegroo said, “but I don’t remember being around when it happened.”

Later that night, that same black-and-red banner would be seen again—in the column of marchers chanting for dead cops.

As the #turnuptheanger contingent got moving, they started with calls to “off the pigs.” Then a tweet records that “black bloc”—a name anarchists often use for themselves—“smashed up a cop car with a cop in it, forced to abandoned car.” That tweet came from Shay Horse, whose bio lists him as an independent photojournalist with ties to Occupy Wall Street. In another post from the same night, Horse uses “Black bloc” to refer to marchers carrying the “No Cops No Prisons” banner who ”broke threw [sic] the barricades and are throwing trash and glass bottles in the street.”

Another anarchist-leaning Twitter account also attributed the ugliest anti-police rhetoric to the #turnuptheanger contingent at the protests.

In this exchange, @Foundersgirl blames “Obama supporters” at “Sharpton’s rallies” for “death to cops” calls. @Anarchonatheist—who had earlier said “those pigs were thugs” about the murder of two police officers—corrects her. “That chant was done by the #turnuptheanger contingent at the millions march,” @anarchonatheist tells @Foundersgirl.

The owner of the original video of the “dead cops” chant told me it was taken on 32nd Street between 5th and Madison avenues.

TMOC’s own social-media posts never place it on that block. But they do put it right around the corner near the time the video was shot.

A tweet from another account using the #turnuptheanger hashtag puts the group two blocks away from the location of the “dead cops” chant.

If they were involved, it’s not clear whether they were acting alone or in concert with other groups.

Whether screaming for murder of civil-service workers constitutes incitement or an anarchist group’s full use of free speech is another open question—the New York Civil Liberties Union didn’t respond to a request for comment in time to be included in this story.

But TMOC wasn’t just hurling violent slogans. The same night the “dead cops” chant was recorded, two police officers were attacked on the Brooklyn Bridge.

When the officers approached a protester who they say was poised to throw a metal trash can, a group of activists surrounded them in a skirmish that was captured on video. Both officers were scraped up, and one had his nose broken, according to the police department.

On its Facebook page, TMOC said that some of its "comrades" surrendered to police on charges of alleged involvement in the altercation.

“As of 9am on Saturday, December 20, comrades of the Trayvon Martin Organizing Committee-NYC have surrendered to the custody of the NYPD, for their alleged involvement in an incident on the Brooklyn Bridge on the night of the Millions March,” reads the letter, which was also posted to the website of The New Inquiry, a left-wing politics and culture magazine known for hosting salons in Manhattan.

“We know they are the victims here—not the NYPD. We are all victims at the hands of the white supremacist, capitalist state,” the letter continued. “For the same reason, we are the ones to overturn it.”

And from there, the letter asked for money for a legal defense fund.

There are not many TMOC members willing to openly admit that they’re part of the group, so it’s impossible to gage TMOC’s demographics. The defendants in the Brooklyn Bridge case, it’s worth noting, are mostly white, while the pictures associated with the group online show a more racially mixed crowd.

It would be interesting to find out more about the radicals whose slogan is “shoot back.” What we know now is that, out of the people arrested on the bridge, one is a Harvard-educated poet and another was making more than $100,000 a year working for one of the most the most powerful unions in New York City.

There are conservatives arguing that the essence of these protests is a call for dead cops, while liberals like New York Rep. Charlie Rangel deny that it happened at all.

It happened and it was a group of maybe 200 in a movement that has drawn tens of thousands in New York alone.

Monday, two days after two police officers were murdered by a disturbed man looking to kill cops, New York’s Mayor Bill de Blasio called for a moratorium on protests. He was joined by New York City Councilman Jumaane Williams, a vocal critic of police policies, who said Monday, “I personally believe there should be a day or two or three moratorium out of respect for the officers that were executed.”

It’s possible to agree with the mayor’s call for a halt to protests and also feel that it’s a shame.

You can criticize the broader New York protests movement’s aims, or call out protesters for failing to publicly and unequivocally condemn violent factions in their midst. And you can acknowledge that while the killer of two cops may have been mentally disturbed, he would have had no problem in recent months tuning into a vengeful frequency directed at police officers.

There are no moratoriums on the Internet, least of all for news of human misery. On message boards and social media, people were cheering and justifying the police murders almost as soon as they happened.

“Good riddance. Whenever I hear about bitch ass police getting murked I celebrate with no fucks given,” someone posted on “thehoodup” message board. “Alot of ppl was not fine with this peaceful protesting shit out here.it didn’t change anything.This dude sent a message to nypd,” the following poster added. In the ten pages of commentary, if anyone felt differently they were in the clear minority.

This birthday card style message was posted ‏by @Loot_Back on the day the police officers were ambushed in Brooklyn.

The same @Loot_Back account was tweeting photos from the #turnuptheanger contingent that had called for dead cops. The Twitter acount links to a webpage advertising the “ultras. An association of antagonists, young, angry and disciplined,” whose anarchist jargon apparently finds its milder expression in cartoon giggles over dead cops.

These violent messages appeared online and in the streets before the police were murdered and continued after. But you can’t reduce the mass protests in New York to a call for killing police without ignoring how that particular message had to be smuggled in.

Political factions obsessed with government saboteurs and false-flag operations had to conspire to manipulate the larger movement around them. To give the truth its rights, you have to see that groups like TMOC were threatened by peaceful protest. For them, this city wasn’t angry enough.

Update: Trayvon Martin’s family sent a statement exclusively to the The Daily Beast rejecting any association with the “Trayvon Martin Organizing Committee” and “its unauthorized use of our son’s name recently to carry a message of violence.” Read the full story here.

Editor’s Note: this story has been updated with new information about online anti-police messages, and to clarify the nature of the Trayvon Martin Organizing Committee NYC’s relationship to people recently arrested for allegedly assaulting New York City police officers.