By Dave Savini

(CBS) — They were a happy couple, recently married, and then a powerful painkiller took his life.

It is a drug so dangerous, it has never been approved, but anyone can buy it easily online.

As 2 Investigator Dave Savini reports, it is killing both adults and children.

Kate Knapp sings at church to help ease the pain of losing her husband. Michael Knapp was 31 years old when he collapsed July 6, 2016, in their Bloomingdale home.

He overdosed on a synthetic pain-killing drug called U-47700.

“I was too late,” Knapp says. “I couldn’t resuscitate him.”

The same drug — with the street names U-4, Pink or Pinky — is suspected of recently killing two 13-year-olds in Utah.

DuPage County Coroner Rich Jorgensen says the drug, which is another form of Fentanyl, is turning up in autopsies across the country. After more than 50 deaths so far, that number keeps growing.

“One mother said her son got a package in the mail, went upstairs, she heard a thud. She went upstairs, and her son was dead,” Jorgensen says.

Knapp says the drug is easy to get: “He went on a Web site, paid $40.”

The painkiller is normally ordered online; often made by drug cartels; and usually shipped from China. A battle is ongoing to shut down the flow to the U.S., says Chicago DEA head Dennis Wichern.

“We have agents right now in China working with the Chinese government to stop it,” he says.

U-47700 was originally created in the 1970s by a pharmaceutical company. At eight times the strength of morphine, it is considered so dangerous, the U.S. Food and Drug Administration never approved it as a painkiller.

“There’s no legitimate use, no medical necessity,” Wichern says. “You are playing Russian roulette with a six-shooter with all the bullets in it. The odds are bad, very bad.”

“It’s very difficult to understand why, why,” Kate Knapp says. “He’s not here. It’s realizing that over and over and over.”

Knapp says her husband battled addiction from his youth and overcame it in many ways. She did not know he ordered the U-4 online and it was the first time he took it.

Knapp has since created a non-profit, called Michael’s Refuge.

The DEA was able to “emergency schedule” U-47700 as an illegal drug, which took effect last week and lasts for two years while they investigate further.

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