Daniel grieved with his best friend's family. Then he said something only her killer would know.

At 19, Jessie Blodgett had the world at her feet.

She dreamed of becoming a choir director, of using music to heal the world. A fierce advocate for animal rights, environmental protection, and ending violence against women, Jessie loved deeply and without reservation.

Her story had barely begun.

On the night of July 14, 2013, Jessie returned home to Hartford, Wisconsin, after celebrating with her Fiddler on the Roof castmates. She wished her mum, Debra "Joy" Blodgett, goodnight around 1am.

The next morning, Joy peeked into her daughter's room on her way to work. Jessie appeared to be sleeping peacefully.

When a piano student arrived at lunchtime and Jessie still hadn't stirred, Joy went to wake her daughter.

Jessie was unresponsive in her bed.

Jessie Blodgett was just 19 when she was murdered. Image: The Love>Hate Project.

Frantic, Joy called emergency services. Paramedics talked her through CPR as they raced to the scene, but it was too late.

According to police documents, officers declared Jessie dead shortly after arriving.

Jessie lay in her bed, dressed in a t-shirt, underwear and sweatpants.

But the marks on her neck and wrists told a sinister story.

An autopsy revealed the horrifying truth: Jessie had been bound and strangled to death.

The next day, Jessie's parents held a vigil at their home. Her tight-knit drama group gathered to mourn, including Daniel Bartelt — a classmate, former boyfriend and seemingly devoted friend.

"At this point in time, nobody knew who the killer could be," Jessie's friend Ian said in a recent episode of Investigation Discovery's A Killer Among Friends.

"It became tough to conceptualise who could have done this thing."

When police called Daniel in for questioning, no one was surprised. He'd grown close to Jessie again recently and her father Buck welcomed him into their home.

Jessie was a passionate performer and singer who wanted to change the world. Image: The Love>Hate Project.

Buck told ID: "Jessie and Dan sat together at school; he was a straight-A student... they would write songs together and sing together. He was welcome in our home."

"He was just over, the day after Jessie's murder, sharing hugs and memories and tears with us until his phone rang and he was called in for questioning."

Ian echoed the sentiment: "We couldn't picture Dan being the type of person who did this."

But Daniel's carefully constructed facade was about to crumble.

The mask slips.

The investigation took a crucial turn when police connected Daniel to another attack.

Just days before Jessie's murder, a woman had been assaulted by a stranger with a knife.

According to police documents, Daniel initially denied involvement but eventually confessed, claiming he'd only meant to "scare" the victim.

During questioning about Jessie's death on July 17, Daniel maintained his innocence. He described their renewed friendship over the past two months, admitting he hoped for something more despite having a long-term girlfriend.

Then he made a fatal slip.

According to ID, Daniel told detectives that someone had "raped and murdered" Jessie.

The problem? Police hadn't released the fact Jessie had been raped to the public yet.

They knew they had their killer.

Image: YouTube/TMJ4 News.

Daniel's alibi, reading and writing alone in a park, quickly fell apart.

A search of nearby rubbish bins revealed a horrifying stash: a cereal box stuffed with strips of duct tape, various ropes, electrical and masking tape, antiseptic wipes, and a blood-stained SpongeBob towel.

Most chilling of all was a homemade ball gag attached to one of the ropes.

Forensic analysis confirmed the ropes matched the marks on Jessie's body, consistent with hog-tieing.

Daniel's computer searches painted an even darker picture: serial killers on Wikipedia, lists of killers ranked by victim count.

DNA evidence sealed his fate.

Daniel Bartelt was sentenced to life without parole. Image: WISN ABC.

Finding forgiveness.

People reports after a 16-day investigation, Daniel was arrested and charged with Jessie's murder.

In August 2014, he was convicted and sentenced to life without parole. He continues to maintain his innocence.

In court, Buck delivered a powerful victim impact statement speaking of how loved his daughter was and how, despite everything, he did not hate Daniel.

"Dan, I forgive you, as I have every day since I learned it was you," Buck said.

"I believe there is good and bad in every one of us, so I do not demonise or vilify you. That's too easy."

Addressing the evil that had consumed Daniel, Buck continued: "This was a monumental loss for evil and a stunning win for love.

"You stole Jessie's life and future, you had power and dominion over her body for a few minutes, but never for one second did you have one ounce of power or control over her spirit, her heart, her will, her grace, her beautiful goodness, and her deep love," he said.

Even in his grief, Buck offered Daniel a path forward: "As long as you are alive, you still have a chance to own what you did, try to make amends, and bring healing into our sick world.

"I hope you take that chance."

Feature image: The Love > Hate Project.