An American woman was killed and five people injured as victims were selected at random in a “spontaneous” knife rampage in central London.
A 19-year-old Norwegian national of Somali origin was yesterday arrested on suspicion of murder after the attack on Wednesday night.
Scotland Yard said no evidence has been found of radicalisation or anything to suggest the man in custody was “in any way motivated by terrorism”.
Assistant Commissioner Mark Rowley said: “Whilst the investigation is not yet complete, all of the work we have done so far increasingly points to this tragic incident as having been triggered by mental health issues.
“At this time, we believe this was a spontaneous attack and that the victims were selected at random.”
The suspect, who has not been identified, emigrated from Norway in 2002, a spokesman for the country’s ministry of foreign Affairs said.
All of the work we have done points to this tragic incident as having been triggered by mental health issuesMark Rowley
Investigators have made “urgent progress” in five strands of work, Mr Rowley said – interviewing the suspect, speaking to his family, witness accounts, address searches and a full intelligence review by police and security services.
Officers have searched an address in north London and will search another in south London.
Mr Rowley, Britain’s most senior counter-terrorism officer, said: “I emphasise that so far we have found no evidence of radicalisation that would suggest the man in our custody is in any way motivated by terrorism.”
The episode took place in a popular tourist spot near the British Museum in Russell Square.
Police raced to the scene at 10.30pm on Wednesday after reports of a man attacking people with a knife.
Mr Rowley, the country’s lead counter-terrorism officer, said armed officers arrived within six minutes of the call, adding: “The man was Tasered and he was detained.”
No shots were fired.
A woman, Darlene Horton, 64 was pronounced dead at the scene while two other women and three men were hurt. Those injured are Australian, American, Israeli and British. Two remain in hospital.