A teenager who admitted to killing a US tourist and injuring five others during a mass stabbing in London's Russell Square has been detained indefinitely.

Zakaria Bulhan,19, from Tooting in south-west London, pleaded guilty to the manslaughter of retired teacher Darlene Horton following the "frantic" attack last August, but denied murder on the grounds of diminished responsibility.

Bulhan told police he was in the midst of a psychotic episode when he launched the rampage and attacked his victims. He killed 64-year-old Horton by stabbing her in the chest.

Horton, a retired special education teacher and mother-of-two, was due to fly back to her hometown of Tallahassee, Florida, with her husband the day after she was killed. She had been in London with her husband while he took part in a summer teaching programme.

A 67-year-old British man, a 59-year-old American man, a 23-year-old Australian woman, a 40-year-old Australian man and an 18-year-old Israeli woman also suffered non-life threatening injuries during the stabbing.

Bulhan was arrested by police following a short chase resulting in officers firing a Taser when they saw he was still holding a knife.

He appeared at the Old Bailey on 6 February to plead guilty to lesser charges of manslaughter by reason of diminished responsibility and five counts of wounding with intent to cause grievous bodily harm, which were accepted by the prosecution.

Bulhan, a Norwegian of Somali descent asylum seeker who arrived to the UK with his mother in 2002, has now been locked up indefinitely at Broadmoor secure mental hospital.

Zakaria Bulhan,
Zakaria Bulhan pleaded guilty at the Old Bailey to the manslaughter of 64-year-old Darlene Horton Met Police

Detective Inspector Tony Lynes, of the Met's Homicide and Major Crime Command, said: "Bulhan's actions caused an enormous amount of fear and distress with initial concerns this incident 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.

"I would like to commend our armed officers who were called to the incident that night not knowing what they might encounter. They arrived on the scene within six minutes and acted with the utmost professionalism to detain an armed and violent man with the minimum necessary force and without firing a single shot.

"However, our thoughts must remain with Bulhan's victims who were simply enjoying a night out on a summer's evening when they were subjected to this terrifying ordeal. And of course the friends and family of Darlene Horton who so sadly lost her life."

One of the police constable's involved in the Taser incident, who had only been a firearms officer for five weeks at the time of the incident, described the moment officers managed to detain Bulhan.

The officer, who did not wish to be named, said: "There came relief that we had managed to stop him without using lethal force and the operation was a success but then sadness and the wind knocked out of our sails with the news one of the casualties had died.

"It was very frightening and the first serious incident I had dealt with as a firearms officer, a bit of a baptism of fire. You are always hoping you won't have to use lethal force but you know what your job is. Mental health is one of the most difficult situations you can deal with as a firearms officer, what are they going to do next, what am I going to do next if they don't respond.

"Thankfully, we were able to resolve this situation without the use of lethal force which has to be the best possible outcome to a situation like this."

Russell Square knife attack
Darlene Horton was fatally stabbed during the random attack in Russell Square London Metropolitan Police