Sydney School Murder: New Details Emerge about Killer's Actions

Sunrise host Nat Barr has raised chilling questions in the wake of Lilie James' tragic murder - as new details emerge about her killer.

Paul Thijssen, 24, is believed to have bashed Ms James, 21, to death with a hammer in the gym bathroom at St Andrew's Cathedral School in Sydney's CBD last Wednesday after she called off their brief relationship.

After Thijssen killed his ex-girlfriend, it's believed he then used Ms James' phone and pretended to be her to text her dad, Jamie, telling him to come and pick her up from the school where she worked as a water polo coach, Daily Mail Australia understands.

Thijssen later phoned police to confess before plunging to his death from the cliffs above Diamond Bay in Vaucluse in Sydney's east.

The only reason he would have sent that message was to get the father to attend the school - either to find Lilie or be there when the police found her, according to criminologist Xanthe Mallett. This raises questions about whether others attending the scene could have been in danger.

Police divers recovered Thijssen's body from the rocks below, leaving his high-flying corporate parents with a difficult decision regarding funeral arrangements.

Thijssen, a former student at St Andrew's Cathedral School, returned to Australia to work in the school's sports department and joined a local hockey team. His whirlwind romance with Ms James began five weeks ago but was short-lived, leading to a confrontation on the tragic evening.

The shocking details of this brutal crime have left Australia shaken, with many unanswered questions remaining.

It is yet to be determined if Thijssen's funeral will take place in Australia or if his body will be transported back to the Netherlands.