The as yet unexplained killing on a central London street of a United States national Wednesday evening is being used to justify a massive build-up of armed police throughout the UK.

London’s Metropolitan Police named the victim as Darlene Horton, 64, who died at the scene. She was the wife of a university professor from Florida, who was within hours of flying home.

It is understood that Horton was attacked by a 19-year-old Norwegian national of Somali origin near the Imperial Hotel, Russell Square. The man stabbed two other women and three men in the incident. Those stabbed were taken to hospital. None had life threatening injuries and three were discharged Thursday. The injured are British, American, Australian and Israeli.

Shortly after the killing, the police arrested the man on suspicion of murder, after stunning him with a Taser. According to the police, the attack took place just after 10:30 p.m. After being called, the specialist firearms police officers who Tasered and apprehended the man were on the scene in six minutes.

Initially, the police stated that terrorism could have been factor in the attack. Assistant commissioner Mark Rowley said, “Early indications suggest mental health is a significant factor in this case and that is one major line of inquiry.” He added, “But of course at this stage we should keep an open mind regarding motive and consequently terrorism as a motivation remains but one line of inquiry for us to explore.”

“As a precautionary measure, Londoners will wake up this morning to notice an increased presence on the streets of officers, including armed officers today,” Rowley said. Later police said they would be on the streets “for as long as we need.”

Rowley’s statement was changed later Thursday morning to omit any mention of terrorism as a motive. Metropolitan Police Commissioner Bernard Hogan-Howe did not reveal any further details about the arrested man or a possible motive, stating only, “As we have already made clear, mental health remains a substantial focus for our investigation.”

He too concluded his statement, “Across our capital today you will see more police officers, armed and unarmed, to reassure the public after recent events overseas.”

Around midday, after an initial investigation that included house searches, Rowley issued another statement saying, “I emphasise that so far we’ve found no evidence of radicalisation that would suggest the man in our custody is in any way motivated by terrorism.”

Despite this, armed police units continued to patrol many of the capital’s busiest locations and tourist spots, brandishing weapons including semi-automatic carbines, Glock pistols, Taser stun guns, CS spray and batons. The Guardian noted, “Around the British Museum in Bloomsbury, near the scene of Wednesday night’s attack, patrols could be seen on almost every street, as well as in the courtyard in front of the museum.”

The units have access to an array of other weapons, including shotguns.

The police blitzing of the capital came just one day after the Metropolitan Police announced Operation Hercules, under which 600 armed police officers, masked and clad in all black body armour resembling paramilitary squads, will flood London’s streets. This will bring the total number of armed police operating in the capital to 2,800.

The units have access to BMW F800GS motorbikes capable of speeds of 140 mph as well as vans. They will operate speedboats that will be deployed all over the Thames. Just hours before the attack Wednesday evening, some of the armed units were paraded before the media, with Sky News shadowing a high-speed boat full of masked police as it speeded down the Thames.

The mobilisation of this force is part of the Conservative government’s plans to increase by 1,500 the number of armed police officers throughout the UK.

Operation Hercules was launched by Hogan-Howe, who said Sunday that the UK’s “threat level” remained at “severe”—meaning an attack was “highly likely.” Citing terrorist attacks that have occurred recently in several European cities, the commissioner said, “You could say it is a case of when, not if ... as the police officer in charge of preventing such an attack, [I] know that you want me to reassure you. I am afraid I cannot do that entirely.”

The launching of Operation Hercules was carried out with the full backing of London’s Labour Party Mayor, Sadiq Khan. It was then endorsed Thursday by Labour’s Shadow Chancellor John McDonnell, the main ally of the party’s nominally “left” leader Jeremy Corbyn.

From the Met’s statements, there is every indication that the London attacker is mentally ill. Yet without any public discussion, vast numbers of armed police have been placed on the capital’s streets.

Due to the gutting of vital social services, many mentally ill people are being left to fend for themselves. The Guardian reported Thursday, “Mental illness is a significant part of what Metropolitan Police officers deal with every day and they get 600,000 calls about it a year. They are called to far more incidents involving mental health problems than robbery or sexual offences, a report by the mental health charity Turning Point found in 2013.”

Turning Point’s report cited a Metropolitan Police Service review that “estimated that 15 to 25 percent of incidents are linked to mental health. Using this estimate the daily contact rises to a minimum of 1,626 calls per day …”

As in London, incidents involving mentally disturbed people and actual terrorist attacks are both used to deploy armed police and the military in capital cities and towns across the continent.

In France, a state of emergency has been in place since terrorist attacks last November. Following subsequent attacks in Paris and the still unexplained killing of 84 people in Nice, more than 120,000 soldiers and armed police have been deployed nationwide.

Huge police mobilisations are ongoing in the Belgian capital, Brussels, and Amsterdam, the capital of the Netherlands. This week armed police flooded Schiphol airport, just five miles from the centre of Amsterdam and the fifth busiest airport in Europe. This was in response to an undefined “threat.” As part of the operation, military police searched every car entering the airport.

In Germany, the coalition government led by Chancellor Angela Merkel has responded to recent events in France and Germany with plans to place soldiers on the streets of the capital, Berlin.

Defence Minister Ursela von der Leyen announced that regional police forces and the Germany army (Bundeswehr) would begin practising co-ordinated exercises on the pretext of training for terrorist attacks. This is in defiance of Germany’s constitution, which after the horrors of fascism, places restrictions on the use of troops on German soil. Since the Second World War, soldiers have only been deployed on German streets to deal with natural disasters such as flooding.

The routine deploying of masses of police armed to the teeth and of soldiers testifies to the extraordinary level of social and class tensions in Europe. No aspect of daily life is now exempt from intrusive policing by the state. In France, dozens of summer events have been banned in Paris, Nice, Marseilles and other towns and cities on the pretext that large crowds could serve as a magnet for terrorists. On Monday, France introduced sea patrols on passenger ferries to and from the UK. For the first of these operations, police officers were flown in by helicopter onto a ferry just as it entered French waters.

Justifying the resort to such repressive measures, Defence Minister Jean-Yves Le Drian stated, “We are in a situation of war. Sometimes it is necessary to ban events if the security requirements are not respected. Everyone must understand this situation leads to constraints.”

Accustoming the population to accept such “constraints” is a major, overarching concern for Europe’s ruling elites. Measures that will be used to target working class protests and strikes are being rolled out in the name of combating terrorism.