A manhunt is under way after a young female staff member, Lilie James, was found dead in the gymnasium at a private school in Sydney’s city centre.

Police said on Thursday they were looking for a 24-year-old male employee, Paul Thijssen, from St Andrew’s Cathedral School after 21-year-old James was discovered with serious head injuries inside the gym toilets.

Emergency services were called to the school about midnight after receiving reports of concerns for the woman’s welfare.

Superintendent Martin Fileman said police were presented with a “confronting” scene when they arrived at the school due to the severity of the staff member’s injuries.

A crime scene was also set up near a coastal reserve at Vaucluse, in the eastern suburbs, where investigators found items linked to the killing.

Police helicopters and boats were patrolling the coastline off South Head on Wednesday morning and Supt Fileman said detectives had been looking into the possibility the man, also in his early 20s, had taken his own life.

The two knew each other but investigators were still working to establish the nature of their relationship, he told reporters.

Daily Mail Australia have reported James was in a ‘secret relationship’ with Thijssen for a matter of weeks leading up to her death. Her friend said the relationship had only recently ended.

Detectives are talking to witnesses and also combing CCTV from the school to piece together what led to the killing.

Supt Fileman said the circumstances of the death would also be confronting for students as it involved school staff.

“We’re currently working in with the school to ensure the welfare of the students and they have measures in place to make sure those students are taken care of,” he said.

The school will be closed to all students until next week except for those sitting year 12 exams.

“An area of the school, not accessible to students, is a crime zone, and we await the approval of police before bringing everyone back on site,” a school spokesperson said.

“The only students onsite are those sitting exams, and we ask that the media does not seek to interrupt their concentration or state of mind as they sit exams that are significant for their graduation.”

Police and the school said there was not believed to be any ongoing threat to students or the wider public after the attack.

School counsellors will be on site for parents and students as required.

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