Members of ISIS forums are encouraging “lone wolf” bomb attacks in some of America’s most high-profile tourist locations: New York, Las Vegas and Texas.

A post in an ISIS message board, created three weeks ago and resurfaced in the last 24 hours with renewed urgency, includes a comprehensive guide to building pipe bombs using easily obtained materials like match heads, sugar and Christmas lights. Titled “To the Lone Wolves in America: How to Make a Bomb in Your Kitchen, to Create Scenes of Horror in Tourist Spots and Other Targets,” the post suggests attacking Times Square and Las Vegas in particular, but also says tourist sites in Texas and metro stations throughout the U.S. would make good targets.

At a boat naming ceremony for fallen cops in Brooklyn on Tuesday, NYPD Commissioner Bill Bratton spoke directly about Vocativ’s story.

The commissioner acknowledged that the online tutorial aimed at provoking an American attack—was a major turn for the new terror organization.

“This is the first time ISIS has used this medium to inspire a “lone wolf” type attack,” Commissioner Bratton told reporters, speaking specifically about ISIS forums encouraging attacks inside U.S. Cities, including “The Crossroads of the World” Times Square.

“We are quite concerned, as you would expect, with the capabilities of ISIS much more than Al Qaeda ever was able to project their ability to use social media to try and spread their recruitment efforts and try to inspire.”

Commissioner Bratton acknowledged that the threat of ISIS inspiring bloodshed on U.S. Soil is being considered as plausible.

“This is a new world, if you will, the evolving world of terrorism–and we are staying ahead of it.

“We have been focused on it and I believe we are as prepared as any entity can be to deal with the threats,. But the reality is that we are living in a new era of potential terrorism. That is the reality.”

The post—spotted in an ISIS forum by Vocativ’s deep web monitoring software, Verne—includes images and detailed instructions reproduced from the summer 2010 edition of an English-language Al Qaeda magazine called Inspire. The section from the magazine was created for an English-speaking audience, and was jovially entitled “How to Make a Bomb From the Kitchen of Your Mom,” with a credit to “The AQ Chef.” The guide was allegedly used by the Tsarnaev brothers to carry out the Boston Marathon bombings in 2013, and it highlights the destructive efficacy of making a bomb using a pressure cooker. In the forum, the English post was re-translated back into Arabic.

Times Square appears in the document, mentioned as one of the most identifiable U.S. tourist spots, and thus a prime terror target. AL Platform forum

The post describes the necessary bomb-making ingredients as being easy to obtain, easy to dispose of quickly and difficult to detect, even by police sniffer dogs. It goes into detail about how to pack the bomb with shrapnel-like pieces of metal for maximum effect, what kinds of casings to use depending on where the bomb will be deployed, how to ensure the safety of the bomber and where to place a bomb to create the most carnage. They also advise would-be bomb-makers on how to cover their tracks so as not to leave evidence on the device. The conversation initiated by the post appears to involve knowledgeable individuals with a strong desire to spread their know-how to others.

Vocativ spoke to several experts in the homeland security and explosives fields who say that while the bomb-making recipes are rudimentary and far from novel, they are potentially viable.

A veteran law enforcement and bomb expert, who spoke to us on the condition of anonymity, says the directions posted on the forum are basic but potentially lethal.

“This is a viable [bomb] recipe,” the bomb expert says. “It happens to be accurate stuff. The person has a working knowledge of explosives, and it’s consistent with what we’ve seen before out of the Al Qaeda and the Arabian Peninsula and their publications.”

However, he explains that the instructions themselves aren’t breaking ground. “This is not new information or new techniques. Save for the excerpt in the beginning, this is consistent with what’s been around since the 1960s or 1970s,” he says. The Anarchist Cookbook was famously published in 1971, for example, including instructions on how to make rudimentary bombs. Many similar manuals exist online today.

While the techniques are generally not new, the pointed nature of the discussion underneath the cut-and-paste manual is worrying, he says.

“The techniques aren’t what worries me,” the expert says. “The fact is they could start going on making these at home, and the forum seems to encourage and motivate would-be bomb makers, including suggesting possible targets,” he says.

“I personally prefer the evening congestion,” one forum user says in a lengthy post describing how to blend into and disappear amid crowds.

Some of the claims discussed in the forum are far-fetched. For instance, one forum user suggests a way to produce powdered chlorine to add a chemical element to a bomb, which (although scary-sounding) falls far short of being actionable, according to experts consulted by Vocativ.

Similarly, chemistry professor and explosives expert Jimmie Oxley, from the University of Rhode Island, tells Vocativ: “They’re trying to explain how to make a device the same way poor man’s James Bond, as I call them, Do It Yourself books did. “

Oxley says these sorts of home-baked bomb-making recipes have been bartered online for years.

“If you look a number of websites in English, you can see kids passing back and forth their favorite [bomb] recipes all the time.”

The post may have been posted online in the hope that some disaffected individuals, perhaps inspired by but not linked in any formal way to ISIS and their recent acts, may take the initiative of making an unpredictable strike on a U.S. target—much like the Tsarnaev brothers did in Boston. Lone wolves, acting on inspiration but without affiliation to overseas groups, are much more more difficult for authorities to track, and their behaviours are therefore unpredictable.

The comments below the bomb-making contain a mix of congratulations and Q&A. “There is no stronger [chemical] agent from this agent?” one user inquires. “I have heard that you can make yellow explosive powder from boiling two liters of chlorine.”

The bomb-making instructions posted on the AL Platform Media forum showed how to fashion, set and test a small detonation timer, among other things.

The conversation also highlights the potentially serious intent of these users. “How many people can be killed if you use the pipe in the size we see in the example and if all the conditions are right and the victim is close to the bomb? One person or two or more?” asks one user. “The number of victims will be higher if there will be more agent,” says another.

The identify of the user who uploaded the information is not known. He has written 160 other posts on the forum, all in Arabic, and seems to be an average user, who has only been a member of the forum since July 2014.

In response to the post, one user shares that the same method provided by the forum was used by the Tsarnaev brothers in the Boston Marathon bombings in 2013, although they tweaked the formula a bit to widen the potential radius of damage.

“Yes this exact method was used by the brothers Tamerlan Tsarnaev and Dzhokhar Tsarnaev (God will release them) in Boston bombings, but they used a pressure cooker filled in fireworks powder and metal pieces.”

An improvised bomb explodes near the finish line of the Boston Marathon on April 15, 2013. Two simultaneous explosions ripped through the crowd at the finish line of the marathon, killing at least two people and injuring dozens. REUTERS/Dan Lampariello

The discussion continues, focusing on how to deliver the message to American groups, both as targets and as potential collaborators.

Says one user: “We must bring the idea to the Muslims inside America and target their forums and their personal accounts. The people of America know their country and their population best. Please translate this to English and bring it to the Muslims inside America, and don’t forget to attack the Jewish, Zionist and freemasonry interests—people and institutions and buildings, for example economic, media and culture [institutions].” Another suggests that there may be potential for recruiting among the “angry blacks,” possibly referring to rising racial tensions in the wake of the Ferguson riots, in the hope of peeling off some disaffected members of society.

The post was first published three weeks ago, but was resurfaced Saturday afternoon around the same time ISIS released the video of David Haines’ beheading on the very same forum, perhaps in the hope that the increased attention would help it catch the eye of a stirred-up opportunist. This comes one week after an ISIS-affiliated account tweeted threats against Twitter employees in the U.S. and Europe, calling on individuals to take initiative and attack.