U.S. Attorney James Kennedy announced Tuesday a 27-year-old former nurse, Kelsey Mulvey of Grand Island, has been charged with stealing medication from Roswell Park.

"Law enforcement officers and medical professionals work in positions of trust, that's why when that trust is broken this is such a big deal," said FBI Buffalo Special Agent in Charge, Gary Loeffert.

Between February 2018 and June 2018, investigators say the nurse gained access to these drugs through a medical dispenser called the Pyxis system. The medicine was meant for cancer patients.

Prosecutors say she was placed on administrative leave last June after a large number of transactions in that system were identified as “canceled removed,” meaning the drawer for the selected medication was accessed but the transactions were canceled.

Kennedy says Mulvey was responsible for treating, but withheld meds from at least 81 patients.

As the former nurse took vials of medication, investigators say she replaced them with water.

In June and July of this year, six patients contracted a waterborne illness as a result.

Kennedy shared how investigators were able to determine Mulvey was the one behind the medication thefts.

“The complaints talk about her carrying a green duffle bag, talks about her being encountered in a locker room at the hospital by another health care professional  and that health care professional spotted needles falling out of her locker,” U.S. Attorney Kennedy added.

Throughout her two years at Roswell, Mulvey sought help through rehab and forfeited her license twice, according to court documents.

"When those efforts fail and the lives and well-being of others are placed in jeopardy and even more vulnerable people are placed in harm’s way, we use the justice system to essentially quarantine these sick people," said Kennedy.

Roswell Park released a statement, which says in part:

“We have taken significant organizational steps to enhance ongoing prevention, detection and response to health care worker drug diversion. These include heightened surveillance with high-tech software, on-campus security features, review and revision of current policy and procedures, and increased staff training and education on what they can do to keep their patients and themselves safe as it relates to drug diversion.”