The billionaire founder and majority owner of Insys Therapeutics was arrested Thursday on racketeering and fraud charges for an alleged nationwide scheme to push an extremely potent opioid drug containing fentanyl onto patients.

According to the Department of Justice, John Kapoor, 74, of Phoenix, Arizona, used bribes, kickbacks, and other fraudulent practices to get doctors to overprescribe the fentanyl drug, called Subsys. Fentanyl is a highly addictive synthetic opioid that can be up to 100 times more potent than morphine. As such, Subsys is only intended to treat severe pain in cancer patients. But according to the DOJ, many patients receiving Subsys didn’t have cancer.

The DOJ alleges that Kapoor, along with six former executives at Insys, paid doctors and pain clinics in various states to write “large numbers of prescriptions.” The department also alleges that Insys used fraudulent means to get health insurance providers to cover the harmful prescriptions.

Last month, a Senate investigation led by Senator Claire McCaskill (D-Mo.), released an audio recording of an Insys representative lying to a pharmaceutical benefit manager in order to get an inappropriate Subsys prescription covered. In that case, the patient—who did not have cancer—later died from an adverse reaction to the drug.

In a statement Thursday, McCaskill responded to Kapoor’s arrest, saying:

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. Anyone, including top executives, who potentially violated criminal law should be aggressively prosecuted.

Acting United States Attorney William D. Weinreb, seemed to heed the call in another statement Thursday, saying:

Today's arrest and charges reflect our ongoing efforts to attack the opioid crisis from all angles. We must hold the industry and its leadership accountable—just as we would the cartels or a street-level drug dealer.

Kapoor, whose worth is valued at $1.75 billion, denies the allegations. His lawyer, defense attorney Brian Kelly, told reporters Thursday that Kapoor "is not guilty of these charges, he intends to fight it vigorously." Kapoor’s bail was set at $1 million and he must wear an electronic monitoring device and surrender his passports, according to the Chicago Tribune.

A spokesperson for Insys told the paper that the company is under new management and has “taken necessary and appropriate steps to prevent past mistakes from happening in the future… We also continue to work with relevant authorities to resolve issues related to the misdeeds of former employees."