Drug company's billionaire ex-CEO arrested in nationwide bribery scam John Kapoor has become the latest former executive to be arrested.

 -- The billionaire who stepped down as head of opioid manufacturer Insys Therapeutics earlier this year has been arrested for his alleged role in a nationwide conspiracy to bribe doctors and others into unnecessarily prescribing the company's fentanyl-based pain medication to patients.

The racketeering, conspiracy and fraud charges against John Kapoor of Phoenix, Arizona, stem from his time at Insys. Six other former executives were charged and arrested in the same case late last year.

Just last month, the mother of a woman who died from using their former company's products told lawmakers, "The only thing that keeps us going at this point in our lives is that the people who did this to my baby will be held accountable for their actions."

In a superseding indictment unsealed in Massachusetts today, authorities allege that after Insys launched a fentanyl spray called "Subsys" in 2012, Kapoor and Michael Babich, another former top executive at Insys, "quickly grew dissatisfied with the success of the drug," which was intended to be used by cancer patients.

So for the next three years, the company looked to bribe doctors into prescribing Subsys "outside the usual course of their professional practice," the indictment alleges. "The defendants and their co-conspirators used bribes and kickbacks to try to cause practitioners to issue new prescriptions for the Fentanyl Spray, as well as increases in the dosage, and volume, of existing prescriptions for the Fentanyl Spray."

According to authorities, the bribes and kickbacks took different forms, including food and entertainment, speaker fees and money for marketing events.

However, while bribes helped propel doctors to issue new prescription for the fentanyl spray, insurers "were reluctant to approve payment for the drug when it was prescribed for patients without cancer," so the company started misleading insurers and agents "into authorizing payment for the Fentanyl Spray," the indictment says.

Last month, Deborah Fuller told a Senate roundtable in Washington that "losing a child is agonizing, but then learning that [daughter] Sarah died from a drug that she should never have been prescribed has caused us so much more anguish and outrage."

"Learning of the massive fraud in which Insys was engaged to get people like Sarah to take Subsys really has made us question humanity," she added.

She said Insys called Sarah's health insurer "pretending to be calling from her doctor's office and the like, telling the insurance company that Sarah needed Subsys because she had cancer and was suffering from breakthrough cancer pain."

"That call was Insys' death wish for our daughter in exchange for profit," Fuller said, adding that the online pharmacy filling the prescription "would look the other way and deliver a carton of deadly fentanyl directly to Sarah's doorstep."

"I believe that Sarah's death certificate should be changed to indicate her death was a homicide and the cause of death should be changed to 'corporate greed,'" Fuller said.

The roundtable last month was hosted by the top Democrat on the Senate Homeland Security Committee, Sen. Claire McCaskill, D-Missouri.

After news of Kapoor's arrest today, McCaskill issued a statement, saying: "Evidence from our investigation suggests that Insys was engaged in systemic fraud and took actions that directly harmed their own customers and public health as a whole. This company has repeatedly gotten away with fines that amounted to a slap on the wrist for actions that helped fuel a nationwide epidemic that's claimed hundreds of thousands of American lives."

--ABC News' Tom Shine contributed to this report.