"You know what I always do? I walk up to the door, turn around and see how perfect my cell looks," NFL star Aaron Hernandez tells his mother during a call from the prison where he was serving a life sentence for the 2013 murder of Odin Lloyd, a football player who was dating his fiancée's sister. A charge later joined by the death of two men during a shooting in 2012.

Curiously, a few days after being acquitted of the latter crime, on April 19, 2017, he hung himself in the same cell that he described as "cozy," causing a stupor among the guards who were watching him and who had expressed their surprise at how quickly the player adapted to prison life, almost as if he had always lived there. 

After the autopsy, a new shocking fact: Aaron Hernandez was suffering from a severe case of CTE, a fairly common brain disease among football players that could have affected his cognitive ability. But to what extent did this severe trauma play a role in the actions he committed? 

This is one of the questions that "Killer inside" tries to answer, the new documentary that Netflix released on Wednesday, and that revises in three episodes the rise to fame and subsequent fall of the Hispanic sportsman, collecting testimonies from family and friends, recordings from his prison calls and his trials, and comments from experts.

Born in Bristol, Connecticut, the New England Patriots star's childhood was no bed of roses; he suffered the wrath of an abusive father who died when Hernandez was 16, his brother Jonathan says in the documentary. But he managed to go to the University of Florida, had a great season playing football and when the New England Patriots signed him and he blew up in the Super Bowl in 2012, his contract was worth $40 million. 

For Patrick Haggan, prosecutor in Hernandez's second trial for the 2012 shooting, the player was an emotional time bomb, not only because of the CTE - which was only discovered after his death and could explain his propensity for violence and impulsiveness - but also because of his tragic childhood. 

"The seeds of this tragedy had begun many years before," he says in the documentary. "He was able to go from being an extremely jovial, nice, friendly, somewhat affectionate guy to becoming angry and violent the next moment." 

Haggard also adds that this is an unusual case because although "people talk about O.J. Simpson being a retired football player who was involved in a series of acts of domestic violence, we have never seen this kind of crime before."

"No one has ever allegedly killed two people, and then played a whole season as a professional athlete."

Dan Wetzel, executive producer of "Killer Inside" and a columnist for Yahoo Sports, is even more emphatic about the multifaceted nature of Aaron Hernandez's character. 

In an interview with Mass Life, he defines him as "a chameleon" with a "double life:"

"He talks to his mother in a certain way. He talks to his fiancée in a different way. He talks to his old football friends in a totally different way, with a totally different slang," he told Mass Live. "He talks to the people he might have been within that dark part of his double life in a different way... That's why those phone calls (the ones he made in prison) are so important. You can ask yourself if this guy is really a bad guy or not, or if he's cheating on me the same way he cheated on other people."

In fact, the sociopathic Hernandez who remains cold and indifferent while in prison contrasts with the "other" Hernandez who phones his girlfriend asking her to send him Harry Potter books, or his mother begging for money. 

Who was Aaron Hernandez? Why did a man who had everything lose his life as if it were a ball that someone kicked off the field?

Watch "Killer Inside" and draw your own conclusions...