Przybycien encouraged Brown to go through with the suicide, even providing running commentary as he recorded her last moments on video, according to court documents.
Now, Przybycien, 18, is being charged with first-degree murder in her death.
If convicted, he would face a minimum of 15 years in prison.
Prosecutors say Brown wouldn't have killed herself, if not for Przybycien's involvement, which they say he boasted about in texts and interviews. His defense, however, says the charge goes too far, and it was Brown and Brown alone who ultimately ended her life.
'It's like getting away with murder!'
Both the prosecution and defense agree that Przybycien was involved in Brown's death. Investigators found that he purchased rope and compressed air and drove Brown to the Maple Lake Campground, where she killed herself. The site is about 15 miles south of Spanish Fork, where Przybycien lived, and about 25 miles south of Provo, Utah.
Przybycien tied the rope into a noose and recorded Brown for more than 10 minutes, according to court documents, as she stood on a rock formation with it around her neck, inhaled compressed gas and finally slipped off the rock to her death.
Investigators say they recovered texts that show Przybycien had thought about Brown's death beforehand and discussed it with a friend.
"What do you do if you knew a friend was trying to commit suicide?" he texted a friend on April 19, two weeks before Brown's death.
"Talk them out of ut (sic)" came the reply, according to documents.
Przybycien continued: "The thing is.. I wanna help kill them. It be awesome. Seriously im going to help her. It's like getting away with murder! Im so f****** up. I'm seriously not joking. It's going down in about a week or two."
When Brown got ready to kill herself, prosecutors say Przybycien did nothing.
"At no point did the defendant offer assistance to save (the girl's) life or render aid but rather he can be heard commenting that her body should be depleted from any oxygen," court documents read.
'I helped her ... I feel so guilty'
The same day that Brown died, Przybycien texted his friend again.
"Bro It happened," he said. "I helped her do it too and I feel so guilty."
Authorities didn't find Brown's body until the next day after hunters in the area alerted them. According to a statement from the Utah County Sheriff's Office
, Przybycien approached officers at the scene and said "he knew this girl and had been with her when she died."
"Through further investigation detectives learned that this man ... had purchased several items used to facilitate the death of the 16-year-old victim. Other evidence at the scene included a cellphone recording made by Przybycien of the 16-year-old girl as she died," the sheriff's office statement said.
Once in custody, court documents say Przybycien told authorities he "felt guilty for the role he played in (the girl's) death," but that helping her die "was my plan."
Court documents also reveal that Przybycien returned to the site of Brown's death the morning after -- when he encountered police -- to retrieve the noose for what the prosecution called "sentimental value."
When does a suicide also become a murder?
To understand the twists and turns of such an unusual case, it's important to know a few things about Utah law. First, there is no second-degree murder charge in Utah, so first-degree is the only type of murder charge.
There is no assisted suicide law in Utah, so that is not an option for the prosecutor. Przybycien is also charged with desecration of a body, a misdemeanor.
"It's a unique case for our state since assisted suicide is not a crime here," Utah County prosecutor Chad Grunander said, noting a judge had to determine there was probable cause to go forward with a murder trial.
"Because the probable cause standard at preliminary hearings is low, and because all reasonable inferences are viewed in a light most favorable to the State, the Court finds there is reasonable belief that (Przybycien's) conduct meets the elements of murder," 4th District Judge James Brady wrote in his ruling this week.
Defense attorney Greg Stewart said Przybycien's team is looking to show that the teenager's actions did not directly cause Brown's death.
"An act or conduct that 'causes' the death is required in all cases -- something like pulling the trigger on a gun, driving recklessly, etc.," Stewart said. "Tyerell picked Ms. Brown up from work when she called and asked for his help, drove her to stores to purchase rope and compressed air for inhaling, and helped her to tie a noose and build a pedestal to stand on. None of these actions directly 'caused' the death of Ms. Brown."
"Her putting the noose around her neck, stepping onto the pedestal and inhaling the compressed air so she passed out and slipped from the pedestal caused her death," he said.
Stewart said Przybycien intends to enter not guilty pleas at an arraignment next week but adds that "nothing has been decided about how we'll proceed in this matter."
Similar case in Massachusetts
If this case sounds familiar, it's because it comes a few months after a watershed verdict in a suicide in Massachusetts.
In June, Michelle Carter, 20, was found guilty of involuntary manslaughter in the suicide of her boyfriend, Conrad Roy, two years earlier. A judge found that Carter's encouragement and participation in Roy's death warranted the conviction. She was sentenced in August to 15 months in a Massachusetts jail -- but will remain free pending appeals.
Though the charges, state laws and court systems differ, the two cases share some similarities.
Carter wasn't physically present as Roy died of asphyxiation while pumping carbon monoxide into his truck, but she was on the phone, allegedly until his last breaths. She also counseled him on how to go through with the suicide and actively encouraged it. This lead-up, like in the Przybycien case, was all captured on text messages.