They tell their victims they're torturing their loved one, threatening to kill them if money isn't sent immediately.
It's all a lie, but victims of the common "virtual kidnapping" scam call it terrifying.
The scam is now growing, which is why the FBI has launched a national campaign to educate people.
The threats are traumatizing and brutal, meant to instill panic.
"They talk about how they're going to cut off a child's fingers. We've had a lot of reports where it's pretty much a dramatic display of screaming in the back ground, maybe saws," said Special Agent Michelle Lee with the San Antonio FBI.
In the past, the FBI found inmates in Mexican prisons were targeting people with Hispanic last names along the Texas border. Now, the dynamics are changing.
"We're seeing individuals of varying ethnicities, regardless of their surnames, that they're being targeted, it appears randomly and throughout the U.S. including Puerto Rico," Lee said.
Lee said there's evidence that more organized crime groups are following suit, mimicking the same scam. She has talked to American doctors who have become a big target.
"I had a physician who said he had a panic attack when he received that call, that they were so believable. He did share with me his concern that particularly older folks could have a heart attack," Lee said.
Most calls are random and scammers play off information they hear on the other line.
"Like if the victim hears someone screaming and they say, 'Mary is that you?' They'll use that information and say, 'Yes we have Mary here and we're going to kill her if you don't send us money,'" Lee explained.
In more rare, sophisticated schemes the callers will first search for personal information about future victims on social media, taking advantage of over-sharers. They find what kind of car people drive, when they're going on vacation, where they live or when they'll be out of pocket. For example, if they're a student posting about taking a long test, it becomes obvious they'll be out of contact with people for hours. It would be hard for family members who got that scam call to see if that person was really were okay.
Lee said knowing all the scammers' tactics could prevent people from emotional stress and losing money.
The callers typically ask for $1,000 or $2,000.
The FBI's new national campaign is asking people who have received these calls to come forward and report the call, even if they didn't fall for it.
This way, they can get a more comprehensive look at the criminals' locations, tactics, and profiles.
The number to call is (210) 225-6741.