
Probe: Scotland Yard believe Zakaria Bulhan, 19, pictured, a Norwegian national of Somali origin who moved to the UK in 2002, was not 'motivated by terrorism' but its officers are trawling his possessions for extremist material.

Counter-terror police will today forensically study computers belonging to the Russell Square knifeman as a neighbour claimed the 'impressionable' teenager could have been inspired by ISIS.

Scotland Yard believe Zakaria Bulhan, 19, a Norwegian national of Somali origin who moved to the UK in 2002, was not 'motivated by terrorism' but its officers are trawling his possessions for extremist material.

But neighbour Parmjit Singh, a BBC radio DJ known as 'DJ Precious' on the Asian network, said he had known 'impressionable' Bulhan for seven years, adding: 'His mental health problems are a scapegoat.'

The 36-year-old said: 'They said he had mental health issues but that was not the boy I knew.

'The news of his mental illness is completely new, we never heard that. Honestly, I think his mental health problems are a scapegoat.'

Asked what he thought motivated the attack, Parmjit said: 'I think peer pressure, hanging around with gangs. He wasn't working, he was hanging around with Somalian boys and I think they had possible links to serious ISIS people - not directly, but they see all this stuff and are inspired by it.

'Why would he attack an American woman tourist in a random attack? I think boys have put pressure on him to go there and do something. He was very impressionable growing up'.

Police are guarding the council flat in Tooting he shared with his mother and siblings as they investigate his motives for murdering American Darlene Horton, 64, in front of her husband Dr Rick Wagner.

The retired teacher was stabbed in the back with a kitchen knife and bled to death on the pavement in the frenzied six-minute attack on Wednesday evening that left five others injured.

A police source said: 'We are expecting counter-terror officers this afternoon who will take away his computers and electrical equipment to study.'

Retired teacher and keen tennis player Darlene Horton, 64 (pictured), was due to return to America today with her Florida professor husband Dr Rick Wagner but was stabbed to death by a Somali-born knifeman in the Russell Square attack

Aftermath: Witnesses heard screams and rushed to windows to photograph the victim's body, which had been covered by a white sheet

Murder: This is the spot where the woman in her sixties died on pavement in Russell Square which was still covered in blood this morning

Captured: Chanel Britton, 19, of Barnsley, captured the moment the 19-year-old Somali teenager who came to the UK from Norway in 2002, was pinned down by police

Tributes: Flowers have piled up on Russell Square, pictured today, where much-loved Darlene Horton lost her life on the final day of her break in the UK

Search: Police continue to work in Bulhan's south London council flat today - a family friend said the emergency services have been called several times this year because the teenager wanted to harm himself

Friends have described their shock at the knife attacks, describing him as a 'teacher's pet' and a 'devout Muslim' who would love debating religion.

Online postings show a man named Zak Bulhan is interested in Islamic study, and in another he pledges support to former Guantanamo Bay inmate Moazzam Begg.

A former school friend said: 'I can't believe it, I'm just telling myself it must be a mistake. We used to get really competitive over grades in maths and debate religion all the time.

Theory: Parmjit Singh, a BBC radio DJ known as 'DJ Precious' on the Asian network, said he had known 'impressionable' Bulhan for seven years, adding: 'His mental health problems are a scapegoat.'

'He was a devout Muslim and he would passionately defend it, but he respected my opinion too. He was a bit socially awkward but as far as I knew he didn't have mental health problems.

'He wasn't the jock but he wasn't the kid who ate glue at the back of the class. He just flew under the radar.'

Today a family friend claimed the teenager had tried to kill himself three times this year before he stabbed to death an American tourist in front of her 'absolutely devastated' husband.

Bulhan was arrested on suspicion of murder after dozens of armed police – fearing a terror attack – brought him down with a Taser stun gun.

Mother-of-two Darlene Horton, 64, was stabbed in the back with a kitchen knife and bled to death on the pavement in the frenzied six-minute attack on Wednesday evening that left five others injured.

She had chosen to stay in London for an extra day to enjoy time in the capital because psychology professor Dr Richard Wagner had taught at a UK summer school for several weeks. They were due to fly back six hours after her murder.

Today it has emerged that Bulhan, who was held miles from his south London home clutching a knife, appears to have been depressed and had tried to kill himself three times in the past six months, family friends have said.

One told The Times: 'He has been very unwell. He wanted to kill himself. I saw his mother with an ambulance outside their flat and she said Zac had called it because he wanted to hurt himself. He's called the ambulance about two more times because he was feeling unwell. His mother was very afraid'.

His local mental health trust have not commented on his case, but it is understood he was living at home not in care. They are working with detectives

Ambulances were repeatedly called to the council flat he shares with his mother and sister in Tooting because the teenager had wanted to harm himself, it has been said. One neighbour had claimed that his parents' separation may have upset him and he had become more reclusive in recent years.

Murder victim Ms Horton had been due to fly home to Tallahassee, Florida, yesterday, and a colleague of the couple in Tallahassee, said her heartbroken husband was 'absolutely devastated.'

The keen tennis player's last words were 'he's still here, he's still here' as she tried to warn others of the attacker's presence before she fell unconscious.

She could not be saved, despite the best efforts of paramedics, and was pronounced dead at the scene. Witnesses said her shocked husband sobbed nearby as her body lay sprawled on the pavement overnight.

Dozens of flowers have been left at the spot where she was stabbed including bouquets with an American flag.

John Thrasher, president of Florida State University (FSU), where Dr Wagner teaches, said: 'There are no words to express our heartache over this terrible tragedy. We are shocked that such senseless violence has touched our own FSU family and we will do all we can to assist Professor Wagner and his loved ones as well as his friends and colleagues in the psychology department as they mourn.'

Fight for life: Emergency services tend to the American woman who would later die from her injuries

Searched: Officers pinned the suspect to the floor and checked him for other weapons before also checking him with a torch

Evidence: A forensic expert analyses the knife used by the attacker during the mass stabbing, which is unlikely to be terror related, police say

Terror: The body of a woman in her 60s is taken from the scene at Russell Square this morning where a knifeman killed her as she walked along the street

Friends of the couple and their two grown-up children back home in the US have described a 'fine family', who played a big role in the university's psychology faculty and were highly regarded within their local community for their philanthropy.

Neighbour Jane Marks told the Tallahassee Democrat that Ms Horton was 'absolutely lovely. Just one of the nicest, sweetest family focused people who is very happy in her space and place.'

The couple are understood to have supported the Tallahassee Memorial HealthCare Foundation - a non-profit community healthcare organisation - as well as a theatrical group and a humane society.

Zakaria Bulhan, 19 (pictured as a schoolboy), moved to the UK from Norway in 2002, and was said to be suffering possible 'mental health issues' when he allegedly stabbed his unsuspecting victims in Russell Square

Mr Wagner had been travelling abroad to teach for several years accompanied by his wife, who began her career in education in the 1980s.

Her former colleague told the newspaper Ms Horton had a 'vibrant personality' and 'loved her students and was eager to do whatever she had to do. She would go beyond the extra mile.'

Janet Kistner, a colleague of Mr Wagner at FSU, said Ms Horton, a keen tennis player, was 'just a bright, inquisitive person'.

'We are a faculty that knows everybody as family. It's very much a loss for all of us,' she told the newspaper.

Mary Alice Linzy, a friend of Ms Horton for 15 years, described how she saw reports of Wednesday night's tragedy on Facebook, before her identity was revealed.

'We're just a small little town here and we have this small tennis community,' Ms Linzy told the newspaper. Ms Horton's tennis partners reportedly met at a local country club as usual on Thursday.

'I'm just going to miss her so much. She was an inspiration for me,' Ms Linzy told the newspaper. 'Every time I step on the tennis court now I'm going to be thinking of Darlene. I just cannot believe it.'

As police investigate the murder, it emerged:

19-year-old of Somali origin Zak Bulhan, who came to the UK from Norway in 2002, has been arrested on suspicion of murder after he stabbed six people in Russell Square at around 10.30pm on Wednesday night.

American Darlene Horton, 64, a retired teacher was fatally injured. The others hurt were British, American, Israeli and Australian and all were treated in hospital. Three were discharged. None are critically ill.

Witnesses say killer was slashing 'anyone he could see' with his knife before he was Tasered by police.

Britain's top anti-terror officer Mark Rowley said detectives had considered terrorist motive but now stabbings appear to be 'triggered by mental health issues'. MI5 and MI6 have no record of killer being an extremist

Scotland Yard has sent out armed units to patrol the streets as London Mayor Sadiq Khan urged the public to remain 'calm and vigilant'.

Bulhan's former friends from Graveney School in Tooting, south London, have now revealed how the Chelsea football fan was a quiet boy who was bullied in the early stages of secondary school.

Scotland Yard appear to have ruled terrorism out as a motive for the knife attacks after speaking to the teenager's family, searching his home and speaking to MI5 and MI6.

One friend said: 'He was quite quiet, but had friends. He was a little bullied but nothing too extreme.'

Scotland Yard has said no evidence has been found of radicalisation or anything to suggest the attack was 'in any way motivated by terrorism'.

Victim: Israeli Yovel Lewkowki, 18, was stabbed in the hand by the killer who murdered one and injured five more on Russell Square

Message: In an emotional Facebook post, Yovel pleaded with her friends to make the most of life. 'The last few hours have taught me to appreciate every second'

Pictured here in 2011, the suspect's former friends from Graveney School in Tooting, south London, have now revealed how Chelsea football fan Bulhan was a quiet boy who was bullied in the early stages of secondary school. Others claimed he gave as good as he got

The schoolmate, who went to Graveney School in Tooting, south London, with Bulhan and wished to remain anonymous, said: 'It's one of the most shocking things I have ever heard.

'No-one would have expected that he would turn out like that.

'He was a quiet, nice kid who had banter with people. He was just a nice kid.

'I have seen some reports that say he was bullied but it was just banter - he gave back as good as he got. It was a two-way thing.'

The Somali-born Norwegian national accused of stabbing Ms Horton to death and injuring five others was said to be suffering possible 'mental health issues' when he allegedly launched the shocking mass stabbing.

As well as killing Ms Horton, the knifeman also injured five others including Israeli holidaymaker Yovel Levkowki, 18, who was slashed across the hand as she approached him to offer help after believing he was a victim.

She said she was lucky to be alive after watching the attacker go on to slaughter Ms Horton in front of her eyes.

'I don't know if it's luck or fate but it's a miracle,' she said. 'The woman standing next to me died before my eyes.'

Counter-terrorism police and murder squad detectives worked through the night to find whether the knifeman was linked to Islamic terrorism.

In the early hours yesterday, they raided the South London council flat where he lived with his family, who had claimed asylum and citizenship in Norway before moving to Britain when Bulhan was five.

Neighbours said he had mental health issues and paramedics had been called several times in recent months as he threatened to kill himself. Scotland Yard said it had found no evidence he was radicalised or motivated by terrorism.

Instead senior officers confirmed mental health issues had played a significant role. Doctors are likely to face questions about what steps were taken to safeguard the public.

The horror unfolded at 10.33pm in Russell Square, yards from the scene of one of the 7/7 bombs. Witnesses reported seeing a 'tubby' mixed-race man with a small black-handled knife.

Ellie Cattle, 21, who is staying in a hotel on the square, said: 'I looked out of my window because I heard sirens. I could see police – three police vans – coming down the road, and all I heard was them shouting, 'Put it down, put it down.'

Armed police arrived within six minutes and chased the knifeman before stunning him with a Taser. A weapon was recovered nearby.

Paramedics found Miss Horton slumped against iron railings but she died at the scene.

One of those injured, a man who suffered a stomach wound, was still in hospital in a 'serious but stable' condition last night. The other victims were Israeli woman Yovel Lewkowski, an American man who was stabbed in the chest, and an Australian woman and man.

Miss Lewkowski, 18, posted a photo of her injured arm online and said it was 'obviously some kind of miracle' she was alive.

The attack came on the day Scotland Yard put on a huge show of force with its counter-terrorist firearms officers. It led to police chiefs increasing the number of officers on the streets even further.

Officers continued to scour Bulhan's three-bedroom council flat in Tooting last night. One family friend said: 'They are a nice family, I know that Zak had a few mental problems. Only a few months ago they had an ambulance around in the night.

'His mother said it was because he was threatening to hurt himself. She said, 'Zak's called an ambulance because he said he wants to kill himself.' The ambulance came a few more times after that.'

Ring of steel: Scotland Yard has sent dozens of armed officers on to the streets yesterday, including on Russell Square, pictured, to reassure the public - and protect if there is any other incident

Location: The killer stabbed the woman to death across the road from the famous Imperial Hotel before running around the corner where he was arrested

Parmjit Singh, 36, who lives below the family, said: 'He was a nice kid, very clever and sporty. But they were very reserved, they would only play with each other when playing football and stuff.

'His parents split up some time ago and his sister, who was very Western, became quite religious. I saw him a few weeks ago and he seemed normal, just a bit quiet. His mother seemed strict and you would hear her shouting at the kids all the time.'

Assistant Commissioner Mark Rowley said terrorism had been an initial line of inquiry due to the 'current climate of threat'.