Charles Cullen, 43, told authorities he administered drug overdoses to put "very sick" patients out of their misery over the last 16 years in nine hospitals and a nursing home in New Jersey and Pennsylvania.
"The evidence that we have indicates that may very well be the case," prosecutor Wayne Forrest said. Cullen, a divorced father of two, was charged with one count each of murder and attempted murder, but more charges could follow.
Investigators are examining records at facilities where Cullen worked as they try to document his claims about the other killings. One body has already been exhumed to undergo toxicological tests and Forrest said other exhumations were possible.
Meanwhile, the Warren County Prosecutor's Office has reopened a 1993 probe into the suspicious death of 91-year-old Helen Dean. She had been treated for breast cancer at Warren Hospital, where Cullen worked in the cardiology department from February 1992 to December 1993.
Dean's niece, Sharon Jones, told The Star-Ledger of Newark that her aunt complained that Cullen gave her an unexpected injection on the morning she was to leave the hospital for a nursing home. Dean died later that day, just 30 minutes after she arrived at the nursing home.
If Cullen's contentions prove true, it would be one of the biggest hospital murder cases in recent U.S. history, surpassing that of Robert Diaz, a California nurse convicted of killing 12 patients in 1981.
During a court appearance Monday, Cullen stood and told the judge, "I am going to plead guilty. I don't plan to fight this."
Somerset County Superior Court judge Paul Armstrong urged him to reconsider his plea.
"You have actually qualified and been accepted for representation by the public defender's office," the judge said.
"I understand that your honor, but I wish to rescind that. I don't plan to fight this."
Cullen said he did not want a lawyer, and was held on $1 million bail.
So far, he has been charged with just one murder, reports WCBS-AM's Chris Keating, in the death of a Roman Catholic clergyman who was a patient at Somerset Medical Center. He was also charged with the attempted murder of a 40-year-old woman at the same Somerville hospital.
Prosecutors were notified by Somerset Medical Center officials after the hospital fired Cullen on Oct. 31. An internal review had found questionable lab results involving six of Cullen's patients.
Somerset turned over information on the six cases to the prosecutor's office, said Dr. William Cors, the hospital's chief medical officer. All six patients had "multiple, serious medical problems," Cors said.
"I can categorically say to the patients of this hospital that the medical center has a safe environment, that we identified a problem, that we have a philosophy of doing the right thing," he said at a press conference.
The charges filed Monday involve the death of the Very Rev. Florian J. Gall, vicar of Hunterdon County in the Roman Catholic Diocese of Metuchen, who died June 28 at Somerset. It was later determined that he had died from a lethal and unauthorized dose of the drug digoxin, a heart medication.
The attempted murder charge stems from the discovery on June 16 that a 40-year-old heart and cancer patient had an elevated level of digoxin. The woman recovered from the overdose and was released from the hospital, but died in September.
Cullen had a checkered career and bounced from hospital to hospital. WCBS-TV's Jay Dow reports one unanswered question about the case is how Cullen was able to secure job after job.
In August 1997, he was fired from Morristown Memorial Hospital for "poor performance," a spokeswoman for the hospital's parent company said.
Cullen worked at St. Luke's Hospital in Bethlehem, Pa., from June 2000 to June 2002, and resigned amid allegations that he had at least twice hidden unopened heart and blood pressure medications in a safety bin for used needles, Lehigh County District Attorney James Martin said.
St. Luke's spokeswoman Susan Schantz said the hospital was never subsequently contacted by anyone checking Cullen's employment references. "Had we been asked, we would have recommended that he not be hired," she said.
Cullen had no record of complaints or any disciplinary actions in New Jersey since he obtained a nursing license in the state in 1987, according to Genene Morris, a spokeswoman for the Division of Consumer Affairs.
Cullen also was licensed to work in Pennsylvania since June 1994, according to the Pennsylvania Department of State. His license was in good standing, officials said.
The families of some former patients who died while Cullen was employed at their hospitals are wondering whether their loved ones were among those the former nurse said he killed.
"My mom was in there and diagnosed with a high level of digoxin," Mary Ann Jones, whose mother died at Somerset Medical Center this summer, told the Courier News of Bridgewater for a story in Tuesday editions. "I talked to my brother and sister, and they want this investigated."