London (CNN) -- Security experts are starting to analyze events leading up to the horrific cleaver attack of a man believed to be a British soldier on the suburban streets of London.
One key line of inquiry they'll be following among the many leads: How does this attack relate to other incidents around the world?
CNN Terrorism Analyst Paul Cruickshank says the precedents are not hard to detect. "It's early in the investigation in terms of looking at the culprit and motivation but there's a track record of Islamist extremists inspired by al Qaeda ideology targeting soldiers in the West," he said.
Other areas the security services would look at, he added, would include which groups -- if any -- were behind the attack and whether it was home-grown.
Cruickshank said that there had been plots in the past when attackers had tried to target military personnel: the fact that Wednesday's murder happened near a military barracks in southeast London was significant.
"It's not clear if this particular officer was specifically targeted or he just happened to be walking through this area and was a target of opportunity," said Cruickshank, "but it seems that more than one individual was part of this attack, so this could well have been planned. We just don't know."
CNN affiliate ITN has broadcast a video showing a man at the scene of the attack with bloody hands and holding a meat cleaver, saying: "We swear by almighty Allah we will never stop fighting you." He then continues: "The only reasons we killed this man this is because Muslims are dying daily. This British soldier is an eye for an eye, a tooth for tooth."
Cruickshank cited the plot, uncovered in 2007, to kidnap and murder a Muslim British soldier. Four men plotted to kidnap a solider on leave and then decapitate him in a garage. Parviz Khan, the leader of the plotters, planned to behead the soldier "like a pig" and then post film of the killing online. It is not known if there are any links between this plot and the attack.
Leading al Qaeda clerics have called those who target soldiers in the West "heroes," Cruickshank said. "These are people inspired by al Qaeda ideology in the West," Cruickshank said.
"Hero" was the term militant cleric Anwar al-Awlaki -- who was born and raised in the United States -- had used to describe Nidal Hasan, an American Muslim soldier based at Fort Hood, Texas. In November 2009 Hasan shot and killed 13 U.S. soldiers at the military base in November 2009.
Hasan and Al-Awlaki had communicated on the internet before the shootings at the military base, used at the time by soldiers about to be deployed to Iraq and Afghanistan, Cruickshank said. Al-Awlaki himself was killed by a U.S. drone strike in in Yemen in September 2011.
"The motivation in these past attacks has been the war in Afghanistan and Iraq," Cruickshank said. "For a generation of Islamist extremists in the UK, Iraq and Afghanistan were their formative experiences."
In 2012, Mohammed Merah, a 23-year-old French-Algerian, went on a killing spree that terrorized France and left seven people dead, including three soldiers. Three children were killed when he attacked a Jewish school. He was eventually tracked down to his apartment in Toulouse, southern France, where he was besieged for 32 hours before being killed as security forces stormed the building on March 22.
During that siege Merah told negotiators that he was acting on behalf of al Qaeda. A senior U.S. counterterrorism official later told CNN that Merah was believed to have linked up with Jund al Khilafah, an obscure Kazakh Jihadist group with ties to al Qaeda, just months before the attacks. ]
Cruickshank said the fact that such killings had occurred since foreign troop levels in Iraq and Afghanistan had been scaled back was irrelevant to the attackers.
"The Iraq War is still very much an issue for these people. A significant number of these have been energised by watching beheading videos put out by groups like al Qaeda in Iraq."
Monica Sarkar contributed to this report.