SA Premier Peter Malinauskas addresses alleged Glenunga High School attack threat

Near 100 police officers spent months investigating a young man who allegedly threatened to attack a South Australian high school and even risked their own safety to arrest him, authorities have revealed.

More details of the dramatic investigation have emerged following the 18-year-old’s first appearance in court on Thursday, where prosecutors charged him with two counts of blackmail and one count of contaminating goods for shocking alleged threats against the Glenunga International High School in Adelaide’s southeast.

In court documents seen by NewsWire, police allege the 18-year-old man menaced a woman, “intending to get her to submit to a demand, namely systemic changes at Glenunga International High School,” between last November and February this year.

It is further alleged the man “menaced a covert operative, intending to get him to submit to a demand, namely payment of 153.71744299 bitcoin and money in the amount of $2,599,500,” between February 19 and May 14 at Glenunga and other places.

He also allegedly “made it appear that food, namely yoghurt, juice jelly, hot cross buns and apples had been or were about to be contaminated with lead acetate,” with the intention of causing prejudice or apprehension on public health and safety.

At court on Thursday, prosecutors said the man - whose identity has been suppressed - had also made threats towards Jews and spectators at Adelaide’s AFL Gather Round and the Fringe festival.

He was remanded in custody and will appear again in court on December 12 for a charge determination hearing.

SA Police Acting Commissioner Linda Williams, speaking on Friday morning, said a “significant investigation team” - including members of ASIO and the joint counter-terrorism task force - had been tracking the man.

“Community safety was at the forefront of every decision we made throughout this investigation,” she said.

No terrorism charges have been laid against the man, and Commissioner Williams said the police were not aware of any radical political or religious motivations behind his actions.

South Australian Premier Peter Malinauskas said he was briefed on the matter on May 2.

“This was a major investigation,” he said.

“It was technically extremely complex and the men and women within SAPOL were literally spending countless nights and days working on this matter, and in each and every step of the way, making sure community safety was at the heart of every decision they made.”

“I want to extend my praise and gratitude to all the men and women who have worked on this case tirelessly.”

The man was not arrested at his home and Commissioner Williams said officers had put themselves at personal risk to arrest him.

“It is correct to say there was personal courage shown by police officers involved in the effect of the arrest,” she said.

“In the fullness of time we can talk about it more.”

The commissioner said she was confident the threat had been contained, though ongoing security measures would remain at place in the school.

Mr Malinauskas warned the nature of crime was changing and becoming more complex.

“Often in policing, we see a lot of things happen in an instant that gets a lot of attention, but the nature of policing is changing in the modern world,” he said.

“It’s becoming far more complicated.

“Crimes today, particularly where there is digital elements to it, have great sophistication and technicality, which means the burdens placed on police … is very high indeed.”