A 19-year-old man has admitted stabbing an American woman to death and injuring five other people, including two Australians, in an attack in a London square.
Zakaria Bulhan pleaded guilty in the Old Bailey on Monday to the manslaughter of retired Florida teacher Darlene Horton, 64, by reason of diminished responsibility.
The Somali-Norwegian on Monday also admitted five counts of wounding with intent to cause grievous bodily harm in the attack in Russell Square on August 3 last year.
He had been charged with murder and attempted murder but the prosecution accepted he suffered from paranoid schizophrenia and was undergoing a psychotic episode at the time of the attack.
Those injured included Australian man David Imber, 40, Australian woman Lillie Selletin, 23, an Israeli woman, 18, an American man, 59, and a British man, 67.
Mrs Horton had been visiting London with her husband, Florida State University psychology professor Richard Wagner. They were due to fly home the next day.
Mrs Horton's widower said in a statement: "Losing Darlene, my wife and best friend, under these circumstances is as bad as you might imagine it to be, if not worse. As bad I feel for my loss, I feel worse for the loss experienced by my two daughters."
Mr Wagner said there was an irony to the fact that his high school sweetheart, a former special needs teacher, lost her life to mental illness.
Detective Inspector Tony Lynes of London's Metropolitan Police said Mr Bulhan's actions caused "an enormous amount of fear and distress" with initial concerns they may be linked to terrorism.
"This was quickly found not to be the case and we now know Bulhan was suffering a severe episode of mental health.
"He clearly poses an enormous risk to the general public and I hope he can now get the help he needs," Insp Lynes said in a statement after the guilty plea.
He praised police for responding within six minutes and detaining an armed and violent man without firing a single shot.
When officers identified the knife-wielding suspect nearby they ordered him to drop his weapon, which he did only after being tasered.
He later told officers he had been hearing voices and "the Devil made him kill four people."
Most of the injured were promptly discharged from hospital but the stabbed British man suffered a perforated bowel and spent a week in hospital.
Malcolm McHaffie of the Crown Prosecution Service said expert evidence from prosecution and defence psychiatrists showed Mr Bulhan was suffering from paranoid schizophrenia and experiencing a psychotic episode at the time of the attack .
"For that reason we have agreed to accept Bulhan's guilty plea to manslaughter based on his diminished responsibility and to five counts of section 18 wounding with intent," he said in a statement on Monday.
Mr Bulhan will be sentenced on Tuesday.