While everyone think they already know what went down on the case of Brian Laundrie and Gabby Petito, given how long the case already is, the real reason why the murder took place has been elusive. Some were willing to chuck it to mental disorder or a passion crime, but the real reason has now leaked and it's so much more bone-chilling. 

Radar Online reported that the diary of Petito's murderer-turned-fiancé has been published against the wishes of her parents, revealing the final moments of her life. During their cross-country road journey in Wyoming, he said Petito wounded herself by falling when they were on a night hike. He termed her death an "unexpected tragedy." 

"I hear a splash and a scream, I could barely see," his handwritten note read. "I couldn't find her for a moment, shouted her name. I found her breathing heavily, gasping and [unclear] was freezing cold." 

Laundrie claimed he rescued Petito from the water and saw a "small bruise on her forehead that eventually got larger." He added that she was too hurt to really tell him where she was hurt or injured. 

Before confessing to her murder, Laundrie stated that he did not know the extent of his girlfriend's injuries, only that she was in great pain and he could not bear to see her suffering. He wrote that he ended her life and it was a form of "mercy killing." 

He added that he really thought it was the right thing to do at the time, but he eventually recognized the errors he made, albeit it's already too late since Petito already passed away. He shared that he was really terrified of what he did. 

In his confession letter, Laundrie apologized profusely to Petito's family and revealed he intended to commit suicide make amends. He kept good on his promise. 

Self-inflicted gunshot wound to the head caused Laundrie's suicide. According to the medical examiner, his remains were "gouged" and "gnawed" by stray dogs, coyotes, mice, and raccoons. 

That is precisely what Laundrie desired. He concluded his confession letter with the words:  "I have killed myself by this creek in the hopes that animals may tear me apart. That it may make some of her family happy." 

Laundrie's remains were discovered in October at the Carlton Reserve near his parents' house in Florida. 

On September 19, his body was located in Wyoming's Spread Creek Dispersed Camping Area. She was suffocated to death. Petito also sustained "head and neck injuries due to blunt force." 

Her family hoped the journal would provide light on her demise, but they did not wish for any information to become public. The fact that it has now made way to the media meant it was unintentionally leaked. 

The family attorney for the Petitos issued a statement shortly after Laundrie's note became viral. 

"I'm shocked that within 30 minutes of the time we left the FBI office, the notebook was released. Neither myself nor Joe Petito or Nichole Schmidt, released that from the notebook," Patrick Reilly stated.