Inside Harper Lee and Truman Capote's Friendship

— -- Two of the best-known authors in American literary history started out as best friends.

Harper Lee, who died today at age 89, and Truman Capote, who died in 1984, grew up spending a great deal of time together as young children and, their friendship lasted for decades.

Over time, however, things changed, and the pair grew apart.

It remains unclear if they ever patched their relationship up before Capote's death.

Early Pals

Lee, who was known by close friends and colleagues by her first name Nelle, was raised in Monroeville, Alabama, and while Capote wasn't born there, he became a fixture in her life at a young age.

Dr. Andy Crank, an English professor at the University of Alabama, told ABC News that Capote would spend the summers at his aunt's house, which happened to be on the same street as Lee's father's home.

"A.C. Lee [her father] noticed they would go around and sit in front of different houses and make up stories about what was going on in the houses," Crank said. "So he bought them an Underwood typewriter -- a very clunky typewriter -- but they would drag that typewriter to each house and write up the stories there and then at the end of the day they would present him the stories."

In addition to sharing a love of reading and active imaginations, Crank said that they both felt left out of the rest of their worlds in different ways.

"Truman was very small in stature ... and he was bullied quite a bit. He was obviously not from that community, and Nelle actually became his protector and beat up the bullies on his behalf," Crank said, noting that Lee was known to be something of a tomboy much like the character Scout from her famed novel, "To Kill a Mockingbird."

Staying Connected

Capote left Alabama first and even though she was just one semester shy of completing law school at the University of Alabama, Lee decided to drop out and join her friend in New York City.

Crank said that he believes that the draw of her childhood friend pursuing their joint dream of being writers was too "seductive" to ignore, despite her initial plans to follow her father's career in law.

The pair's connection was put down in words as well. Michael Bibler, an associate professor in English at Louisiana State University, said that they had promised each other to make one another characters in their first books and both followed through. Capote was supposedly the inspiration for the character Dill in "To Kill A Mockingbird" while Idabel from Capote's "Other Voices, Other Rooms" was purportedly based off Lee.

The Turning Point

There are multiple theories about why exactly the once-close pair separated, but most experts speculate that the turning point came after the two became famous.

"He wanted be at Studio 54. He wanted to be a celebrity. He wanted to be on 'The Johnny Carson Show.' He wanted people to pay attention to him," Crank said.

By contrast, Lee became "a virtual recluse" after the immediate success of "To Kill A Mockingbird," he said.

"I think her celebrity frightened her. She was not expecting it," Crank said.

On top of that, Lee supposedly played a big role in the creation of one of Capote's seminal works, "In Cold Blood," and there has long been speculation that Lee was mad that she did not receive credit for that work.

"She went with him and did a lot of interviews and took a lot of notes and he really didn't give her enough credit publicly," Bibler told ABC News.

"It's not entirely clear whether they fell out or they just drifted apart. I suspect somewhere in between," he said.