The church's security alarm rang out at the bush-enclosed property on Greville Street for 10 minutes before an unmarked police auto arrived, neighbour Sharon Schwartz later told reporters.
The alleged attacker was asked to leave the centre "only and exclusively in relation to a domestic incident" Det Chief Insp Jones said.
A teenager undergoing a mental health assessment in a Sydney hospital is expected to be charged after a 24-year-old Church of Scientology member was fatally stabbed at the organisation's Australasian headquarters.
New South Wales police indicated both victims were church employees, but it did not disclose their identities nor their roles.
A Scientologist in Australia was stabbed to death by a 16-year-old boy outside of the headquarters in Sydney.
"At this stage unfortunately the 24-year-old male has passed away and inquiries are being made to contact family", a police officer said, as cited by News.com.au.
He was rushed to Royal North Shore Hospital just after 12.30pm in a critical condition, but later died.
The victim was a 24-year-old Taiwanese staff member who was escorting a 16-year-old boy out after an apparent family dispute. The second man was treated for a minor injury.
Jones said the teenager had a "lawful reason" to be at the Scientology complex in Chatswood, a major business and residential district in the Lower North Shore of Sydney, approximately six miles north of the city's business district.
After his mother told Scientology staff what had happened between them the day before, they chose to move him off the premises, a church source told the Telegraph.
"I came down when the first camera crew showed up but I was told it wasn't a huge deal", he told AAP. "We can not make any further comment beyond the fact that the victim was a beloved member of our church".
"It's a huge building, a lot of people come from around Asia to study here", he said.
It's a closely guarded, secret facility, but the Church of Scientology's Sydney headquarters are now a crime scene.
The sprawling Chatswood complex is described by the Church of Scientology as its "biggest spiritual centre outside the United States".
"It offers a lot of services".
The site - which borders the Lane Cove national park - was snapped-up for about $37 million by the secretive group, who outlaid another $20 million in renovations and construction.