Why did Ted Bundy become a serial killer? Some experts think they know.

Netflix’s new biopic Extremely Wicked, Shockingly Evil and Vile, has thrust serial killer Ted Bundy and his crimes back into the spotlight.

And when watching the story of a man who murdered at least 30 women and described himself as “the coldest son of a b*tch you’ve ever seen”, there’s just one question at the forefront of everyone’s mind: Why would anyone do something so heinous?

Over the years, countless experts have studied Bundy and his crimes to try to find an answer to that question.

Watch the official trailer for Netflix’s Extremely Wicked, Shockingly Evil and Vile below. Post continues after video…

Here are some of the more prominent theories about why Ted Bundy became a serial killer:

1. His childhood.

In another Netflix series, The Ted Bundy Tapes, we heard a lot more about Bundy’s boyhood, which he painted as idyllic.

But according to psychiatrist Al Carlisle, who carried out a 90-day psychological assessment on Bundy while he was in prison, it was actually ‘lonely’ and could be what lead to his ‘psychopathic tendencies.’

Speaking to A&E Real Crime, Carlisle said, “If early in life a person is lonely and doesn’t fit in and is empty, they begin to look for some way to undo that, to satisfy their loneliness. And they turn to fantasy to comfort themselves. This is what happened with Bundy.”

That loneliness may have been partly down to Bundy’s unusual family set-up. According to Investigation Discovery, he grew up thinking his biological parents were his grandparents, and that his mum was his older sister.

According to Carlisle, finding out the truth years later had a big impact on Bundy.

Bundy’s first signs of criminal behaviour were in his teens when he began peeping in windows and shoplifting.

2. A bad breakup.

At the University of Washington, Bundy met his first girlfriend, Diane Edwards, who is often referred to as her alias Stephanie Brooks.

“The relationship I had with Diane had a lasting impact on me,” Bundy said in The Ted Bundy Tapes.

“She’s a beautifully dressed, beautiful girl. Very personable. Nice car, great parents.

“So for a first-time girlfriend, you know, it was really not so bad.”

Ted Bundy with his first girlfriend, Diane Edwards.

Bundy, who often felt that Diane was out of his league, spent a lot of time trying to impress her.

From working for the Republican candidate for Seattle to applying for a number of law schools after college, Bundy tried hard to gain the approval of his girlfriend and her affluent parents.

"She inspired me to look at myself and become something more," he said in the Netflix documentary.

"We spent a lot of time driving around in her car, making out and telling each other how much we loved one another."

But after failing to get into law school, Bundy and Diane's relationship quickly dwindled and over the summer, Diane broke it off.

"She stopped writing [to me] and I started to get fearful of what she was up to. I had this overwhelming fear of rejection that stemmed, not just from her, but everything.

"In there, somewhere was a desire to have some sort of revenge on Diane."

Following their split, Bundy made it his mission to reconnect with Diane. He had a plan for revenge.

Even while he was dating single mother Elizabeth Kloepfer, Bundy continued to try to rekindle his relationship with Diane.

Four years after their split, Bundy and Diane briefly reignited their relationship and the pair often spoke of marriage.

In the end, however, Bundy was just leading her on in a plan to lure her in just to dump her like she had dumped him.

"I just wanted to prove to myself that I could have married her," he said.

In the same year Bundy and Diane ended their relationship once and for all, Bundy began hunting, kidnapping and murdering innocent women.

Weirdly enough, as many criminologists have pointed out, Bundy's victims all had one thing in common – they resembled his first love.

"Ted Bundy was a predator on women who physically resembled Edwards: e.g., young, white, with long dark hair parted in the middle," Ronald M. Holmes wrote in his book Serial Murder.

3. A porn addiction.

The day before his execution in January 1989, Bundy granted an exclusive final interview to Dr. James Dobson, founder of Focus on the Family.

In the interview, Bundy cited a pornography addiction as a possible explanation for what he had done.

"I was essentially a normal person, I had good friends, I led a normal life except for this one small but very potent, very destructive segment of it that I kept very secret and very close to myself and I didn’t let anybody know about it," he said.

Bundy spoke of buying soft core porn magazines in the local grocery store before becoming compelled to find more violent material.

He said: "Like any addiction, you keep craving something harder, which gives you a greater sense of excitement, until you reach a point where the pornography only goes so far."

Bundy described the addiction as an "indispensable link in the chain of behaviour" that led to the murders and assaults he committed and said he'd seen a similar pattern with other violent offenders during his time spent in prison.

"I’ve lived in prison for a long time now and I’ve met a lot of men who were motivated to commit violence just like me and without exception, every one of them was deeply involved with pornography.

"Without question, without exception, deeply influenced and consumed by addiction to pornography."

When Dobson asked about his fate, he said: "I think society deserves to be protected from me and from others like me. That’s for sure."

Of course, the true reason behind what Bundy did will never be known - and absolutely nothing can serve as an excuse.

Ted Bundy was executed at 7:06 a.m. on Tuesday, January 24, 1989, in Raiford Prison in Starke, Florida.

Conversations With A Killer: The Ted Bundy Tapes and Extremely Wicked, Shockingly Evil and Vile are both available to watch on Netflix now.

For more on this topic:

• The untold story of what happened to serial killer Ted Bundy's daughter, Rose Bundy.
• Liz Kloepfer met the love of her life in a bar. He turned out to be Ted Bundy.
• The little-known story of serial killer Ted Bundy's first girlfriend, Diane Edwards. 
• Molly Kloepfer was raised by Ted Bundy for six years. This is what her life looks like now. 
• The faces we should be remembering when we talk about Ted Bundy.