What makes a killer contains graphic details of sexual assault and violence and is not intended for all audiences.

Listener discretion is strongly advised.

June 2010, Cumbria, a predominantly rural county in northwest England, home to the peaceful community of White Haven.

It was about to be shattered by the murderous rampage of one man.

This perfectly ordinary 52-year-old taxi driver had suddenly taken it into his head to shoot everybody in the area.

Over the course of a single day, Derek Bird would kill 12 people and injure 11 more.

He picked people off who were just going about their day-to-day lives and it seemed to make absolutely no sense whatsoever.

I think that was the worst of my life. I wouldn't wish it on my worst enemy.

This callous killer only stopped when he ran out of ammunition and as police were closing in, he turned the gun on himself.

We have a man who had committed no substantial crime in his life who in one moment transformed himself into a spree serial killer.

This is what makes a killer, a series that chronicles the lives and crimes of the world's most notorious killers.

I'm your host, Jennifer Natoso.

In every episode, we'll trace a killer's origins, examine their behavior and follow their path to bloodshed.

In this episode, we'll discuss Derek Bird.

Derek and his twin brother were born on November 27th, 1957 in Enterdale Bridge, a village a few miles outside the coastal town of Whitehaven.

The birds appeared to be an ordinary family. The twins had an older brother and their father worked for the nearby local council.

Derek and his twin brother, David, went to school in Whitehaven.

Despite being slightly older by five minutes, Derek always seemed to be in the shadow of his younger brother, David.

Author and journalist, Jeffrey Wantzel, talks more on their upbringing.

It's always assumed, isn't it, that twins will adore each other. There are many twins that are like that.

But in this particular case, I don't think they were. I think they were rather isolated from one another.

David was probably the more likeable one, Derek the quieter one. It was kind of a bit of a loner.

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