A pensioner went on a vicious "stabbing spree" outside a supermarket, injuring four innocent women, a court has been told.
They were picked at random by Ethem Orhon, who wanted to "get revenge on police for what he perceived as their mistreatment of him", prosecutor Jonathan Polnay told Kingston Crown Court.
Orhon, 67, of Deacons Walk, Hampton, west London, has pleaded not guilty to two counts of attempted murder and two of wounding with intent to cause grievous bodily harm.
The women - Suzanna Brand, 53, Janet Morsey, 63, Jean Sullivan, 68, and Charandasi Chandiramani, 71 - suffered "serious and appalling injuries" in or near the Sainsbury's car park in Hampton, west London, on May 20.
The "true bravery" of two schoolboys - who distracted Orhon, warned others that he was armed and dangerous, called police and stayed on the telephone with the 999 operator during the rampage - potentially stopped further bloodshed, the jury was told.
Speaking of the boys, who cannot be named for legal reasons, Mr Polnay said: "Without their help it may be that more people would have been injured by this man."
Holding up a knife with a 4in blade, Mr Polnay told the jury that Orhon "plunged this knife at least 20 times into four innocent members of the public who had been doing their shopping".
Orhon had been picked up the day before by police outside a public toilet in Kensington, central London, the court heard.
They had suspected he might have drugs but Orhon was found with a Leatherman knife, the jury was told. He was charged with having a bladed article and released on bail.
Orhon went back home, just 10 minutes from the Sainsbury's, and picked up his spare Leatherman knife and went straight back out, the court heard.
He was wearing the same clothes from the day before and carrying a rucksack containing Turkish identification materials, a UK passport, 1,075 euros and £307.87 in cash, the jury was told.
The court heard Orhon later said in a police interview that he had felt "mentally tortured" by police, adding: "I went home and got my other Leatherman. I shouldn't have done it. I feel bad. It was a loss of control. I felt humiliated."