The body of Numan Haider, the man shot dead after stabbing two counterterrorism officers, is removed from the scene of the attack in the suburb of Endeavour Hills on Sept. 24, 2014, in Melbourne, Australia. (Photo by Luis Ascui/Getty Images)

No stolen planes. No complicated plans. No approval from higher-up jihadis in Afghanistan, Syria or Iraq. No need for visas. Just angry men with readily available weapons killing innocent civilians whenever and however they can. There has always been the fear — justified by some experience — of the “lone wolf” terrorist attack.

But now it’s compounded by an explicit call to lone-wolf action by the Islamic State and by the presence of thousands of foreign fighters in Syria. These so-called so-called “tourist jihadis” don’t need visas to return home and make trouble. On the eve of the Jewish Holiday Rosh Hashanah, the world is on edge — particularly Australia.

The Sydney Morning Herald reported Numan Haider, 18, was shot dead on Tuesday after he stabbed two Australian counterterrorism police officers — just days after unprecedented raids in Australia nabbed 15 allegedly linked to the Islamic State. He had allegedly waved an Islamic State flag at a shopping center and posted photographs of himself wearing military camouflage with an Islamic flag alongside an abusive message about the Australian Security Intelligence Organization and the federal police. When he came in to talk with police at their request, authorities said he attacked them with a knife, stabbing two officers. Other officers then shot him dead.

The confrontation followed a call to arms by the Islamic State.

“You must strike the soldiers, patrons and troops of the tyrants. Strike their police, security and intelligence members,” Islamic State spokesman Abu Mohammed al-Adnani said in a videotaped statement released Sunday, as the Associated Press reported. The statement continued: “If you can kill a disbelieving American or European — especially the spiteful and filthy French — or an Australian, or a Canadian, or any other disbeliever from the disbelievers waging war, including the citizens of the countries that joined a coalition against the Islamic State, then rely upon Allah, and kill him in any manner or way however it may be.”

Was he inspired by that? Nobody knows.

“Our members had no inkling that this individual posed a threat to them and as far as we were concerned, it was going to be an amicable discussion about that individual’s behavior,” Victoria Police Assistant Commissioner Luke Cornelius said. The surprised officers had “no choice” but to shoot, he said.

“I think that this attack occurring in the context of the fatwa that came out earlier this week, a fatwa that implored followers to attack infidels and ask no one’s permission, thereby really an incitement to lone-wolf attacks — I don’t think that’s a coincidence at all,” said Australian National University Professor of National Security Michael Wesley.

“Kill him in any manner or way however it may be”: Those are very broad marching orders for potential lone wolves, which is why authorities are hard-pressed to respond to them. In New York last week, for example, security restrictions were tightened ahead of Rosh Hashanah, as they are every year, as well as a United Nations General Assembly in Manhattan.

Police had to look like they were ready for something. They just didn’t know what. It was enough to prompt the Department of Homeland Security and the FBI to alert law enforcement authorities to be vigilant in the wake of the U.S. airstrikes in Syria without specifying some concrete threat.

After all, lone wolves with ideological or religious grievances have attacked in America before. Timothy McVeigh. The Unabomber. The 2009 Ft. Hood shooting.

“When we think about terrorism, the first thing that usually comes to mind is al Qaeda or similar types of groups. Yet the individual terrorist has proven to be among the most innovative, creative, and dangerous in terrorism history,” Jeffrey D. Simon, author of “Lone Wolf Terrorism: Understanding the Growing Threat,” told Time.