Image copyright Met Police Image caption Zakaria Bulhan admitted the charges on the first day of his trial

A knife attacker has admitted killing a US tourist and wounding five others in a rampage in central London.

Nineteen-year-old Zakaria Bulhan carried out the attack in Russell Square on 3 August last year.

Retired teacher Darlene Horton, 64, was visiting the city with her husband when she was killed.

Bulhan pleaded guilty at the Old Bailey to manslaughter on the grounds of diminished responsibility and charges of wounding.

The teenager, from Tooting, south-west London, had been charged with murder and attempted murder, but the court accepted his plea.

The court heard he was suffering an "acute" episode of paranoid schizophrenia at the time of the attacks.

Image copyright Metropolitan Police Image caption Darlene Horton was visiting London with her husband, Richard Wagner, a university professor from Florida

Mother-of-two Ms Horton was due to return home to Tallahassee the day after the attack.

The knife penetrated her left lung and heart when she was stabbed in the back. She died at the scene.

Lillie Sellentin, David Imber, Martin Hoenisch, Bernard Hepplewhite and Yovel Lewronski were all injured in the rampage.

The court heard they have all recovered well from their injuries.

'Unreal experience'

Mr Hoenisch, a retired fireman from Las Vegas, was visiting London with his wife Laurie Kelly when he was injured in the attack.

He said on Facebook it was a "very unreal experience" and he was "still very saddened about the woman who was killed".

Ms Lewronski, 18, who was stabbed in the upper arm, was visiting London from Tel Aviv.

She wrote on the social media site that she did not know whether to call it "luck or fate" that she escaped death.

Media playback is unsupported on your device Media caption CCTV shows police chasing Zakaria Bulhan moments after his attack

Image copyright Rehana Azam Image caption Emergency services were pictured at the scene in the aftermath of the attack

The Old Bailey was told Bulhan had been seen "moving in an erratic fashion" in Russell Square.

"Without warning or provocation, the man stabbed six people in relatively quick succession, saying nothing to any of them, moving on after each stabbing towards his next victim," said prosecutor Mark Heywood QC.

'Definitely me'

Bulhan screamed and ran away when police ordered him to stand still and drop the knife. He fell to the floor when officers Tasered him.

Police said when Bulhan was interviewed, he refused to take part in an identification parade but said: "It was definitely me."

Mr Heywood said the case had been considered "at the highest level" before it was decided to accept his pleas.

His defence said he had an "appreciation of the harm he has caused and of the suffering he has inflicted".

'I came close to shooting him'

A firearms officer has revealed he nearly shot Zakaria Bulhan to try to cut off his escape route following the stabbings in Russell Square.

The officer, who was speaking anonymously, said his first thought when the reports came in was of terrorism as "you hear Russell Square and you think of the [7 July] bombings".

The officer, who had only been in the unit for five weeks, went with his partner to Bedford Place to cut off Bulhan's escape route.

"He was running at pace with the knife raised and kept looking back at us every time we were screaming to stop," he said.

As Bulhan headed towards the British Museum, the officer said a "pre-emptive strike" with a Taser had to be made before the teenager could hurt anyone else.

He said he was "very close" to shooting Bulhan dead, saying: "It had to be a pre-emptive strike. We could not let him get around the corner."

John Jones QC told the court that Bulhan had expressed "complete regret and profound sorrow" for what he had done.

Mr Justice Spencer ordered the attempted murder charges to lie on file.

The court heard that months before the killing Bulhan had dropped out of college because of his mental state.

In March last year he had been referred for treatment for his mental health and his behaviour deteriorated leading up to the August attack.

Bulhan will be sentenced on Tuesday.