Water polo coach Lilie James was killed when her ex-boyfriend Paul Thijssen hit her head with a hammer at least 25 times inside a bathroom at St Andrew's Cathedral School in Sydney.
The 21-year-old had ended her casual relationship with the 24-year-old five days before the attack on October 25, 2023 - a rejection which an expert believes had fatal consequences.
During their two months together, Thijssen was jealous and tried to coercively control Ms James by calling her repeatedly and loitering so she didn't spend time with other men.
Although he couldn't conclude why Thijssen killed Ms James, forensic psychiatrist Danny Sullivan hypothesised he hated his ex-girlfriend for rejecting him and "punished her by killing her".
While Ms James was lying dead in a pool of blood, her ex-boyfriend took her phone and messaged her father Jamie in an attempt to lure him to the school, an inquest was told earlier on Wednesday.
"Don't ask why or call. Please come to the school now and pick me up," the text read.
Her father replied "Are you OK?" and checked the location of her phone, which registered as St Andrew's where she worked alongside 24-year-old Thijssen.
Mr James called his daughter's phone twice but no one picked up. Instead, he received a text saying: "All good just came trouble (sic)".
Counsel assisting Jennifer Single SC said Thijssen was the only person who could have sent the messages to Mr James.
Thijssen later called triple zero saying they would find a body inside a gym bathroom at St Andrew's, but declined to reveal his name or exactly when he had seen the corpse.
When police arrived, the extensive injuries to Ms James' body and the amount of blood in her hair had rendered the body "unrecognisable" and they believed the victim was Asian.
They were only able to identify the 21-year-old after looking at CCTV footage from the school, which was shown to the inquest.
The footage showed an unsuspecting Ms James smiling and chatting casually with Thijssen before walking to the gym bathroom with her swimsuit in hand.
She looked at a sign blocking off one of the bathrooms - which Thijssen had placed there earlier in the evening - before entering the disabled bathroom.
Thijssen followed her and waited patiently outside the bathroom with a hammer in his right hand.
He appeared to look directly at the CCTV camera before lunging into the bathroom two minutes later.
After bludgeoning Ms James to death in a premeditated attack, Thijssen was found dead in Sydney's eastern suburbs hours later.
The inquest is considering whether his death was self-inflicted.
Ms Single noted Ms James was smiling and chatting with Thijssen in her last moments and appeared to show no indication of what he would do.
"No matter how many times you see that footage, it is not easy to watch," she said as her voice broke.
Security footage from earlier in the evening showed Thijssen alternating which hand held the hammer while practising the murder outside the bathroom.
He was also seen disabling the automatic sliding doors, in a move Ms Single said was designed to prevent the school cleaners from disturbing his attack on Ms James.
The inquest into the pair's deaths is also considering broader issues such as coercive control and unacceptable behaviour in relationships in an attempt to prevent similar tragedies.
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