YESTERDAY the French decided to light up the Eiffel Tower in rainbow colours, in solidarity with the American victims of terrorism in Orlando. But before the lights were even switched on, terrorism struck again on French soil. Last night two police employees—one an officer, the other an official—were knifed to death in their home west of Paris by a man identified by the French police as Larossi Abballa. President François Hollande called it “unquestionably” an act of terrorism. Islamic State (IS) claimed responsibility. After two bloody terrorist attacks last year, France is struggling to consider such events the new normal.

The latest attack took place in Magnanville, a residential suburb some 50 kilometres (32 miles) west of Paris. According to the French prosecutor, Abballa stabbed the police officer to death before taking hostage his partner, an official at a nearby police station, along with their three-year-old son. After an elite police squad stormed their home in a burst of gunfire, shooting Abballa dead, they discovered that he had cut the woman’s throat. The child survived. Three other suspects thought to be in his circle were today detained for questioning.

Abballa grew up near Magnanville in Mantes-la-Jolie, a heavily Muslim town that squats beside the motorway and is dominated by brutalist tower blocks. He ran a food-delivery business. He was not only known to French intelligence services, which monitored his phone calls earlier this year, but had been convicted in connection with past terrorist offences. In 2013 Abballa was sentenced to prison for his part in a network of jihadist recruiters linked to al-Qaeda in Pakistan, and served time in prison in France. Marc Trévedic, the anti-terrorism judge who secured his conviction, described Abballa as “unpredictable” and “concealing”, and said that he had clearly wanted to become a jihadi.

The French public prosecutor, François Molins, confirmed that Abballa had sworn allegiance to IS three weeks ago. At his home the police found a list of targets, which included police and prison officers, some public figures, rappers and journalists. In a 13-minute video that Abballa posted on Facebook, before it was taken down, he vowed to “turn the Euro into a graveyard”, according to David Thomson, a French author on jihadism who saw the post. This was a reference to the Euro 2016 football tournament, which France is currently hosting, and which has seen its own share of unusually violent hooliganism entirely unrelated to terrorism.

France is already under a state of emergency, which the government extended in order to cover the month-long football tournament. So the country was more alert than ever to the threat of a terrorist attack. As well as 10,000 soldiers on patrol, 90,000 police and security officers have been deployed on the streets—more personnel than in the entire German army. Yet the Magnanville attack once again underscores the vast difficulty of monitoring would-be terrorist activity, and deterring attacks.

Indeed, after the Paris attacks last year, France came under some criticism for the quality of its intelligence work, since many of the terrorists were known to its own services. Yet events in both Magnanville and Orlando show how hard it is to detect imminent attacks, even when individuals are monitored, if suspects are careful about their public behaviour and communication. Like Omar Mateen, the Orlando shooter, who had been interviewed by the FBI over his links to IS, Abballa had been monitored by French intelligence. Yet, as with the FBI, the French services judged that there was nothing they could detect from his conversations that suggested he was about to launch an attack, the French prosecutor said.

The Magnanville attack also underlines the multi-faceted nature of the terrorist attacks now being carried out in the West. France last year faced home-grown suicide bombers, as well as gunmen armed with an arsenal of powerful weaponry. It has since reinforced perimeter security at transport hubs, stadiums, shopping centres and other public places. Yet unlike the bloodbath in Orlando this week and at the Bataclan concert hall and terrace cafés of Paris last November, Abballa carried out a savage attack with just a knife, forcing himself into the private home of an off-duty officer. No heavy weapons were found at his home. “Another level of horror has been reached,” said Manuel Valls, the French prime minister.

France continues to feel particularly vulnerable. The government reckons that as many as 1,400 French citizens are involved in jihad, either already in Syria and Iraq, waiting to go, or having returned to France. This compares with some 250 Americans, according to the Programme on Extremism at George Washington University. IS vowed to make the month of Ramadan, which began on June 6th, a bloodbath in Europe and America. Patrick Calvar, head of the DGSI, the French domestic intelligence service, recently told a parliamentary commission that France was the country “the most at threat”. Each attack on French soil makes learning to live with that level of threat just that bit harder still.