The killing of a Canadian soldier in broad daylight, followed by a shootout in Parliament. A hatchet attack on two New York City police officers posing for a photo on the sidewalk. The 16-hour siege of a chocolate shop in Sydney.
All carried out, authorities have said, by men inspired by radical Islam and acting on their own. Not directly organized by ISIS or al Qaeda, but achieving their goals just the same — terror, chaos and the promotion of extremist ideology.
On Tuesday morning Australia time, when security forces stormed the chocolate shop and killed a self-styled sheikh who had taken 17 hostages, they brought an end to what appeared to be the latest in a string of so-called lone wolf attacks.
Each attacker may be driven by his own circumstances, personal frustrations or mental instability. The Sydney hostage-taker, identified as Man Haron Monis, had a past that included allegations of sexual assault and an arrest for accessory to murder, and his full backstory is far from clear.
And U.S. officials speaking to NBC News have described at least eight other Americans, most of them young, who were apparently driven to ISIS by ignorance, naïveté or a loss of hope.
But experts on extremism said that the Sydney siege reinforced the lone attacker as a more persistent threat in industrialized countries than a feared replay of Sept. 11 by al Qaeda or mass killings carried out by jihadists returning from distant battlefields.
“They have such a small signature and footprint,” said Thomas Sanderson, co-director of the Transnational Threats Project at the Center for Strategic and International Studies. “They can act whenever they deem fit.”
He drew a comparison to Ottawa, where a convert to Islam named Michael Zehaf-Bibeau killed a soldier at the National War Memorial and fired shots in Parliament in October. He had at most “tangential” links to other radicalized people, authorities said.
In New York, Zale Thompson, who was shot to death after the hatchet attack on the police officers, was described as “self-radicalized” and having visited ISIS-focused websites, but not having acted as part of any organized plot.
And in May 2013, a British army officer was stabbed to death in London by two men who described themselves as “soldiers of Allah,” bent on avenging the deaths of Muslims at the hands of the British military.
Attackers described as lone wolves may be acting with little planning, but that does not mean they aren’t inspired by the ideology of Islamic militants. And both ISIS and al Qaeda have repeatedly put out the call.
Less than three months ago, a spokesman for ISIS, Abu Muhammad al-Adnani, urged supporters in Australia “not to let this battle pass you by,” and to kill Australian civilians or soldiers whenever possible.
Authorities in Sydney described the hostage siege as an “isolated incident.” But the attacker chose a heavily trafficked business district for a target and paralyzed the most populous city in Australia.
And because the standoff went on for the better part of a day, it dominated media coverage all over the world. It may have been a lone wolf attack, but it achieved at least the psychological objectives of organized terrorist groups.
By attracting all-day coverage in American media, Monis seized “the biggest propaganda tool that ISIS could have wished for,” Michael Kay, a former senior defense adviser in Britain, said on MSNBC.
But the attack in Sydney bore another hallmark of the lone wolf terrorist: disorganization.
Some hostages managed to escape during the siege, and Monis “did not seem to have a specific plan for what he wanted to do,” said Laith Alkhouri, the director of Middle East and North Africa research for Flashpoint Intelligence, which consults on global security.
Alkhouri reviewed Monis’ posts on social media, some in English and others in Arabic, and said that it was clear that he was inspired by radical Islam.
On Twitter in November, Monis wondered whether Australia would be part of the Islamic State someday. In another social media post, he appeared to swear allegiance to Abu Bakr al-Baghdadi, the ISIS leader, Alkhouri said.
“There is no explicit link connecting him to any terrorist group,” Alkhouri said. “But his talk has revolved around the caliphate. He has these grievances, specifically, that he voiced out.”
Monis, an Iranian who had been granted asylum in Australia, was a professed spiritual healer and a sexual-assault suspect who had sent threatening letters to the families of slain Australian soldiers. He was also arrested as an accessory to the murder of his ex-wife, who was stabbed repeatedly and set on fire, before he was released on bail. He was known to Australian law enforcement.
The problem is that people like that are all too common, Sanderson said.
“You look at the profile, and there are thousands of guys like this — in trouble with the law, immigrants or asylum seekers,” Sanderson said. “What do you do? Put a policeman on every one? Never leave their side?”
The best authorities can do, he said, is to “shake the cage” — monitor contacts and see what they can hear. Because lone wolves do not belong to an organization, and have not fought on the battlefield, they may “just not be coming up on the radar screen,” he said.
“It’s a massive number of people who are out there,” he said. “It’s hard to detect them — more than any other element of the threat.”