The next little while was a blur. Police and ambulances arrived at the school. Police asked for photos. They took him back to the station. They told him Lilie had been found in the gym toilets, where she’d gone to change for water polo shortly after 7pm. She had been violently, horrifically attacked.

Police wanted to speak to Thijssen. Within hours, he was the prime suspect in her murder.

Jamie plays that night over and over in his head. “I feel like I let her down.” So does Peta. “I’ll never forget that one moment in time when the realisation that she’ll never walk through that door again [dawned. It] will haunt me for the rest of my life.”

None of Lilie’s friends had noticed any red flags about Thijssen, a Dutch-born former St Andrews student, when they began dating five weeks before her death. Sophie Clisdell described him as chatty. “She always liked people who talked a lot because she talks a lot,” she told 60 Minutes. “Just very nice. And he was always very helpful. They’d work together and help each other out.”

Another friend, Kristina Avramis, had met him two weeks before Lilie died, when her friend brought him around to her house. She found him well-mannered and composed. “She liked his vibe, he liked her vibe, and, you know, they just didn’t really want to put a label on anything,” she said.

But one of Thijssen’s former girlfriends had seen a sinister side. It began with small things. “He was, I would say, kind of a bit obsessive; just had a lot of need for attention, was always wanting me to share my location, was really thingy about being in my Facebook and Instagram profile pictures,” she told the program.

After they broke up, and when she refused to get back together, he punched a tree because he “couldn’t punch the one thing I want to”, she remembers him saying. “I was actually fearful for my safety at that point and basically ran back home.”

Then she saw him outside her house two mornings in a row. About 6am, “I look up out of the kitchen window and through the slats in our fence, I see Paul’s face staring at me,” she says. “I scream and my dad comes running downstairs. He grabs a cricket bat and he fully chases him down the street.

“He was unhinged, as if he was in some sort of episode. I don’t even know how to explain it. He looked kind of, um, like deranged; almost like something was not right about him.”

That Wednesday night, CCTV footage captured Thijssen arriving at a reserve in Vaucluse at 8.47pm, not long after he used Lilie’s phone to message her parents. He walked down a path, and dumped a hammer in a bin before driving off. Footage suggests he sat around the corner for two hours, before calling triple zero at midnight to tell police about Lilie. His body was found at the base of a cliff the next day.

The path Thijssen walked along was opposite Lilie’s friend Kristina Avramis’ parents’ house, where Avramis had met him two weeks before. Police were there at 2am. It was her family’s CCTV that filmed him walking.

“I knew straight away it was Paul,” she told 60 Minutes, which is owned by Nine Entertainment (also the owner of this masthead). She identified him to police. “My brain still can’t put into pieces what’s happened.”

No one can. Lilie is gone, and Thijssen’s decision to take his own life hours after he took hers has left those who love her with no answers.

Lilie’s room is as she left it. “We haven’t even made the bed,” says Peta.