The man accused of the frenzied knife attack on a young woman in a busy supermarket is a mental patient who police say struck at random.

Samuel Reid-Wentworth was last night charged with stabbing the 20-year-old victim in a terrifying attack which only ended when shoppers and security guards wrestled her attacker away.

He is due to appear at Worthing Magistrates’ Court today accused of the attack.

The woman, who police say did not know the suspect, was still fighting for her life in hospital last night.

Police spent yesterday scouring the Somerfield store in Avon Road, Littlehampton, in the hope of finding evidence after the attack, which witnesses described as a “living nightmare”.

It also emerged that the 21-year-old suspect, of Longford Road, Bognor, is a psychiatric patient under the care of the Sussex Partnership NHS Foundation Trust.

After the brutal attack on Tuesday afternoon, the victim was taken to Worthing Hospital and later transferred to a hospital in Southampton in a critical but stable condition.

Streaks of blood still mark the point, yards from the checkouts, where the woman was dragged away from her attacker by brave grandmother Bonnie Brown.

The security guard who wrestled the knifeman off the woman, and who did not want to be named, said: “I was just doing my job. It all happened so quickly.

“I hopefully stopped the woman suffering any worse injuries than she already had.

“It was a total blur. To be honest, looking back on it now, I don’t really remember too much but it shocked me quite badly.

“I’ve been told to take the rest of the week off. I want to try to forget about it.”

Although the town centre supermarket was closed all day on Wednesday, the bloodstained aisle where the attack took place remains visible to passers-by through the store’s double glass doors.

The stabbing, which police say was motiveless, is believed to have happened while the victim was queuing to pay for her shopping.

Shelf stacker Martin Howard, 55, who works in the confectionery aisle where the attack took place, said: “It’s a complete shock. You don’t expect this kind of thing to happen here.

“We’ve all been offered counselling. I think most people who saw what happened will need it. It was like a living nightmare, and my thoughts are with the girl and her family.”

Witnesses say the victim was stabbed at least 15 to 20 times before store security staff floored the lone knifeman.

The attacker is believed to have thrown away the weapon, prompting yesterday’s search.

Officers removed thousands of cans and packets of food from shelves, dismantled display units and used telescopic mirrors to search between aisles.

They eventually found a blade wedged between the tinned fruit and frozen goods aisles.

Detective Chief Inspector Jeff Riley, of Sussex Police, said: “This appears to be a random and motiveless attack on an innocent young woman shopping in her local store. As far as we are aware, she was not known to her attacker.”

A spokeswoman for Sussex Partnership NHS Foundation Trust said: “We were very shocked to hear of this terrible incident and our thoughts are with the young victim and her family.

“We can confirm the person who has been arrested is known to our services. However, we are unable to comment any further at this stage because there is an active police investigation under way.”

Anyone with information about the attack is asked to call police on 0845 6070999 quoting Operation Pentney, or Crimestoppers anonymously on 0800 555111.

Sussex Victim Support has also set up a helpline for anyone affected by the incident. Anyone affected should call 0845 3899528.