After the sudden deaths of two patients at a hospital in New Jersey, nobody could have guessed the crimes that were about to be uncovered.

And a key player in the investigation was Amy Loughren – the subject of the new Netflix film The Good Nurse – who would play a vital role in revealing the shocking truth about Charles Cullen, a colleague she called a friend.

Born in New Jersey in 1960, Cullen was the youngest of eight siblings.

His father was a bus driver who died before Cullen turned a year old, and his mother, a homemaker, died in a car accident when he was a teenager.

His first murders

After what has widely been reported as a miserable childhood, a brief stint in the Navy and numerous alleged suicide attempts, Cullen eventually became a nurse, graduating from nursing school in 1987 before getting married.

Cullen and his wife had two daughters before getting a divorce in 1993.

During that time, Cullen is believed to have killed his first victims.

Cullen would go on to work in several hospitals and nursing homes. Some jobs he quit after being investigated over allegations of misconduct – on one occasion because an elderly woman complained he kept coming into her room and giving her injections when he wasn’t the nurse assigned to her.

He was fired from one hospital for hiding heart medicine in a bin meant for disposing of needles.

He would bounce from different medical centres in New Jersey, and even worked for a time in Pennsylvania after getting a licence to practice there.

His weapon of choice: Digoxin

Between 1998 and 2002, he did some agency work and had some full-time jobs.

In this time, he is believed to have killed even more people.

His weapon of choice was a drug called digoxin – a medication routinely used to treat people with an irregular heartbeat or heart failure – but is lethal in large doses.

Cullen would also inject patients’ saline pouches with lethal doses of insulin and other drugs.

His crimes were committed over a period of 16 years – but it was in 2003 while he was working at Somerset Medical Centre in Somerville, New Jersey, that it would all finally unravel.

Florian Gall was a reverend being treated at the hospital.

After showing signs of improvement during his stay, Gall had a massive heart attack and died.

It was later determined that he had a lethal level of digoxin, and his death was caused by an unauthorised dose of the drug.

Cullen was finally arrested in December in 2003.

He told investigators that he administered the drug overdoses to put “very sick” patients out of their misery.

He admitted to 30-40 murders, but the true number is thought to be closer to 400 – which would make him the most prolific serial killer in US history.

The friendship that would ultimately bring him down

While working at what would become his last hospital, Cullen met a nurse – Loughren – and they formed a friendship.

She saw in him a kind man, someone she wanted to spend time with and be friends with.

But it was Loughren – described as “courageous” and “incredible” – who helped detectives build the case against him.

The single mother and cardiomyopathy sufferer was coping with night shifts in a New Jersey hospital in order to qualify for health insurance when the apparently highly-qualified Cullen was hired to help manage the workload.

The two quickly formed a close bond – Cullen even helping Loughren to cover up her illness and care for her two young daughters.

But following the sudden death of two patients, detectives became suspicious of Cullen.

When they gave her documents that showed the drugs Cullen was ordering, she “knew he was murdering people”, she previously said.

“There were so many withdrawals of lethal medications” that you wouldn’t order unless you wanted to kill someone,” she had told CBS at the time.

She began collecting evidence at the hospital and wore a wire at a meeting with him. She also admits to manipulating him to try to get him to confess.

In The Good Nurse, Loughren is played by Jessica Chastain, while Eddie Redmayne picks up the role of Cullen.

Read more:
Jessica Chastain on playing the nurse who helped catch her serial killer colleague

The former nurse has now spoken to Sky News.

She says she was “proud” to see the film come together, although it acted as a “trigger” for so much of the time she spent with Cullen.

Loughren said: “I was pretty terrified every day and I held that together.

“The things that they don’t show in the film was that I was actually much more sick – and I was truly terrified of leaving my two girls behind.

“Watching Jessica play me – I allowed myself to feel proud of myself.”

‘My guilt about missing my friendship – because he’s a monster’

“It was triggering watching Charlie (played by Redmayne) because Eddie truly embodies who my friend Charlie was.

“The way that he moves, the way that he speaks, the interactions that we have, are so real. That part of it was extremely triggering.

“And allowing myself to understand that I missed him for a while – and my guilt about actually missing my friendship, because he’s a monster.

“But I didn’t know the murderer. I only met the murderer a couple of times and he played this part of my friend.

“I missed that friendship, so it was very triggering. And then it was like, ‘let’s get him’.”

Making a film ‘was laughable at first’

Film producers found the relationship between the single mother and Cullen as the most “compelling” part of the narrative.

Loughren, who retired 18 months ago, added: “It was laughable at first because I’m thinking how would anybody really want to see a film? And truly, (the investigation) was such a small part.

“Darren Aronofsky was the one who initially picked it up and decided to make it into a movie.

“He said the most compelling part of Charles Graeber’s absolutely brilliant book was the friendship and that it was compelling to him.

“Something that I had actually been embarrassed about and felt so much guilt about was all of a sudden going to be up on a big screen.

“I didn’t really know how to feel. I didn’t want anyone to know who I was 20 years ago.

“I didn’t want anyone to be judging me from the 20 years ago that I was.

“It was scary. I didn’t want my name on it at first. Then I realised it’s going to happen with or without me – I might as well give myself a voice.”

Chastain, who met Loughren for the first time during a Zoom call, highlighted learning how complicated life was for the former nurse.

‘What she stumbles into is quite shocking’

Chastain told Sky News: “To be able to talk to Amy and understand what her life was like and what she had at stake, it really helped me to realise how courageous she was and what an incredible person she is.

“All the things that she was juggling at the time. Being a single mother, two girls, not having health insurance, working on a night shift so you’re not really getting proper sleep.

“And also, at the same time, needing a heart transplant. That’s what we walk in with at the beginning of this film.

“What she then stumbles into is quite shocking.”

Director Tobias Lindholm said what he “loved” about the story was how it focused on “a hardworking woman whose superpower was her humanity”.

He added: “I remember coming across the script a few years ago and it mirrored Charles Graeber’s book a bit more closely in that it focused on the killer, but it was Amy Loughren’s role in this story that I found to be most interesting.”

The Good Nurse is in UK cinemas and on Netflix.

Listen to Sky News’ Backstage podcast below to hear Chastain speak of her role in The Good Nurse, and you can click here to subscribe to Backstage wherever you get your podcasts