Over the past year or so, the type of crime associated with Bitcoin scammers has evolved in an unpredictable and somewhat frightening manner. While we’re used to seeing stories involving hackers freezing the computers of unsuspecting users and demanding payment in Bitcoin in order to unlock it, a new group of scammers have started threatening deadly violence on their targets.

As noted by The Verge, a number of police departments are alerting the public to a particularly treacherous scam that has targeted users all across the US. Here’s how it all works: a scam artist will fire off an email to someone in a particular building and relay that someone with a bomb is on the premises. The recipient is then instructed to make a large Bitcoin payment — sometimes to the tune of $20,000 — in order to prevent the detonation of the explosive device.

One such instance occurred earlier today in Boston where a number of businesses were on the receiving end of bomb threats. Local police and fire departments — and the bomb squad, of course — were naturally on high alert, though no explosive devices were ever found.

“We are aware of the recent bomb threats made in cities around the country, and we remain in touch with our law enforcement partners to provide assistance,” FBI Boston Division spokeswoman Kristen Setera said in a statement on the matter. “As always, we encourage the public to remain vigilant and to promptly report suspicious activities which could represent a threat to public safety.”

One example of a scam email that has been making the rounds reads as follows:

Good day. My mercenary has carried the bomb (lead azide) into the building where your business is conducted. My mercenary built the explosive device under my direction. It can be hidden anywhere because of its small size, it is impossible to destroy the supporting building structure by this explosive device, but if it denotates there will be many wounded people.

My recruited person is watching the situation around the building. If he notices any suspicious activity, panic or cops the device will be blown up.

I can call off my man if you make a transfer 20,000 usd is the price for your safety and business. Transfer it to me in Bitcoin and I assure that I have to withdraw my mercenary and the bomb will not detonate. But do not try to deceive me – my guarantee will become valid only after 3 confirmations in blockchain.

It is my Bitcoin address: [redacted]

You have to solve problems with the transaction by the end of the working day, if the working day is over and people start leaving the building the bomb will explode.

Nothing personal this is just a business, if I do not see the bitcoin and a bomb explodes, next time other companies will send me more bitcoins, because it isn’t a one-time action.

I will no longer log into this email, I monitor my wallet every twenty minutes and if I receive the money I will give the command to my man to get away.

If the bomb explodes and the authorities see this email We are not a terrorist society and don’t take responsibility for explosions in other places.

Incidentally, recipients of the email above are scattered all across the United States, with some located in Boston, North Carolina, Massachusetts, and Indiana. Again, no explosives have been found, though the threats have resulted in a number of building evacuations.