Discretion is advised.

This is 10-minute murder.

According to the FBI, there's one key difference between a serial killer and a spree killer.

While serial killers have a cooling off period between their crimes,

spree killers typically continue to kill over a short period of time.

Criminal psychologists and investigators have struggled to understand the psychology behind spree killers.

But for many criminals, details about their childhoods can pull back the curtain, providing an

insight into the horrific crimes they commit as adults. For Charles Starkweather, born in Nebraska

in 1938, his resentment of other people was the motivator for his crimes,

and it began to develop at a very young age.

Charles was an unhappy child.

He had a birth defect that affected the shape of his legs, and he claimed that his classmates

bullied him because of his speech impediment.

When he became a teenager,

he fell in love with exercising. And now that he was strong enough, he turned the tables

and started threatening and beating up his bullies. Quote, he could be the kindest person

you've ever met, said one of his school friends. He'd do anything for you if you liked you. He was a hell

of a lot of fun to be around, too. Everything was just one big joke to him. But he had this other side.

He could be mean as hell, cruel. If he saw some poor guy in the street who was bigger than he was,

better looking or better dressed, he tried to take the poor bastard down to his size.

Charles' classmates weren't the only people to notice that he had this dark side.

By the time he reached his late teens, his family was so terrified of his fits of rage

...