The following is a script from "Angel of Death" which aired on April 28, 2013, and was rebroadcast on July 14, 2013. Steve Kroft is the correspondent. Graham Messick, producer.
Tonight you're going to come face-to-face with a serial killer, one of the most prolific in U.S. history. Serial killers don't usually talk to reporters. In fact this story, which first ran in April, was the first time in the 45 years of 60 Minutes that we ever interviewed one.
Charles Cullen was a critical care nurse who admits to killing up to 40 people. Some suspect it was a lot more. The murders took place over 16 years in seven different hospitals. There were suspicions at nearly all of them that Cullen was harming patients, yet none of them passed that information on to subsequent employers. Newspaper headlines called him "The Angel of Death," but as you will see, Charles Cullen was no mercy killer. Until we interviewed him four months ago, he had never spoken publicly about his crimes, never tried to explain why he did it, or even express remorse to the families of victims when he finally faced them in court.
Thomas Strenko: This monster didn't even know us or our son, but had the audacity to end his life.
Richard Stoeker: I'd like to tell you a little about my mother, that you murdered. You don't even have the guts to look this way do you?
Clara Hardgrove: Charles. Why don't you look up at us?! I'd like to show you what you did to our children. This is their dad in his coffin. How do you like that?
This was the scene seven years ago at the Somerset County Courthouse in New Jersey, as Charles Cullen sat through his sentencing hearing, refusing to speak, or even acknowledge the family members of people he had murdered. Even the judge was exasperated.
Judge Paul Armstrong: Mr. Cullen, I asked you a question...Why is it that you have chosen not to address the court?...Can you hear me, Mr. Cullen?"
He's kept that silence behind the walls of the New Jersey State Prison in Trenton, where he is in protective custody to keep him safe from other inmates. Protecting himself from his own demons has been more difficult. We found out when we sat down across from him in a cramped cubicle separated by a thick layer of glass, to talk about the people he's killed.
Steve Kroft: Is 40 an arbitrary number?
Charles Cullen: Forty is an estimate. I gave a number between 30 and 40. I think I have identified, you know, most of them.
Steve Kroft: Look, you pled guilty to murder. But you don't use that word.
Charles Cullen: I think that I had a lot of trouble accepting that word for a long time. I accept that that's what it is.
Steve Kroft: Do you consider yourself a serial killer?
Charles Cullen: I mean, I guess it depends upon a person's definition. If it's more than one and it's a pattern, I guess then yes.
In Cullen's case, all his victims were patients assigned to hospital units where he worked as a nurse. They ranged in age from 21 to 91. Some were critically ill. Others were ready to be discharged when Cullen injected them with drugs that would kill them. It was a pattern that began 26 years ago at St. Barnabas Medical Center in Livingston, New Jersey, Cullen's very first nursing job.
Charles Cullen: I worked on the burn unit. So, I mean, there was a lot of pain, a lot of suffering. And I didn't cope with that as well as I thought I would.
Steve Kroft: And that was the first place that you gave someone medication that caused them to die?
Charles Cullen: Yes.
The patient was John Yengo, a judge from New Jersey, who was suffering from a severe case of sunburn, until Cullen injected him with a fatal overdose of lidocaine.
Steve Kroft: Do you remember the person?
Charles Cullen: I mean, I remember one and that's the only person I've been able to identify.
But there could have been more...St. Barnabas didn't know about the patient Cullen murdered, but it did suspect him of trying to kill or harm a half dozen other patients by randomly and repeatedly poisoning bags of saline solution.