A teenager who killed an American tourist and injured five others when he ran amok with a knife in London's Russell Square could be locked up indefinitely when he is sentenced later.
Zakaria Bulhan, 19, plunged a large kitchen knife into the back of 64-year-old retired special needs teacher Darlene Horton, then "skipped" away with a "crazed smile" on his face, leaving carnage in his wake.
On August 3 last year, Mrs Horton was among many tourists on their way back to their hotels after enjoying an evening meal or shows in London's theatreland.
Initially, police feared reports of indiscriminate violence at the scene of one of the 7/7 bombings could be a terror attack.
It was only later that it emerged that Bulhan, who is of Somali origin, was mentally ill.
Within six minutes of the alarm being raised, armed police swooped on the scene and Bulhan was arrested without a shot being fired.
After being Tasered and bundled on to the ground, Bulhan, from Tooting, south London, was heard to mumble repeatedly "Allah, Allah, Allah".
At the Old Bailey, Bulhan admitted manslaughter by diminished responsibility and five charges of wounding with intent to cause grievous bodily harm.
Prosecutor Mark Heywood QC accepted the pleas following the "highest level" of consultation in light of evidence Bulhan was suffering an "acute" episode of previously undiagnosed paranoid schizophrenia.
Months before the killing, Bulhan, a Norwegian national, had dropped out of college and in March last year he had been referred for treatment for his mental health due to his "odd" behaviour.
Bulhan had gone with his father to attend prayers at the East London Mosque, but had run off and was caught on CCTV heading towards Russell Square where he stabbed six people in quick succession.
Mother-of-two Mrs Horton was visiting London with her husband, Richard Wagner, a university professor from Florida who was teaching summer classes.
She had been out for a last meal with her husband before she was due to return to their home in Tallahassee the following day.
As they headed back to their hotel, she came across Bulhan moving around in an "erratic fashion" and wielding a large knife.
Bulhan plunged the knife so deeply into Mrs Horton's body that it went "right up to the hilt". She died at the scene.
Her husband had shouted: "This guy is trying to stab people," and chased him with his camera phone at the ready to take photographs.
Five more random strangers were injured, but went on to make full recoveries, the court heard.
Bernard Hepplewhite, 65, from London, had been to see a production of Showboat in Drury Lane with a Canadian friend while Australian tourist Lillie Sellentin, 23, was returning from a trip to see Aladdin at the Prince Edward Theatre.
They only realised they had been stabbed by Bulhan when someone shouted: "He's got a knife."
American Martin Hoenisch, 59, returning from a restaurant in Covent Garden with his wife when he suffered the same fate.
Australian David Imber, 40, who had been to see Kinky Boots at the Adelphi Theatre, described the knifeman's "crazed smile" as their eyes locked.
The youngest victim, Israeli Yovel Lewronski, 18, was returning from dinner with her grandfather and began to scream hysterically after Bulhan sliced into her arm.
One of the firearms officers who took Bulhan down said he came "very close" to shooting Bulhan before he could hurt anyone else.
The officer said he was overcome with "relief" at not having to use lethal force, only to have the "wind knocked out" of his sails at finding out that someone had died.
Bulhan could be handed an indefinite hospital order when he is sentenced on Tuesday by Mr Justice Spencer.