A market vendor has described the moment his customers were stabbed in front of him, one of them fatally.
Adam Kadirzadah, who sells fruit in East Street in Walworth, south London, told BBC London how a man approached shoppers from behind.
"It was a nice morning, there were a lot of customers in the market, it was a busy time," Mr Kadirzadah said. "The guy was shouting out with a big knife... It was really shocking, I couldn't sleep all night. It was really bad."
One man was killed in Sunday morning's attack, while a man and a woman were taken to hospital. Their condition is unknown. A man, believed to be in his 60s, was arrested at the scene.
This article contains detail that some may find distressing.
"We had a few customers at my stall, they were buying the fruit for the family," Mr Kadirzadah told BBC London.
He said some people ran away when they saw the man with the knife, adding: "The two customers we had at the front of my stall, they couldn't see it.
"The customer was picking up a lemon and he [the attacker] was stab-stab-stabbing. He stabbed from the back."
Mr Kadirzadah said two of the victims fell to the ground, and the man with the knife fled.
"As soon as he left my stall, a lot of people were running after him to not let him go until the police came," he said.
"Luckily, the police came quick or it could have been more than 20 or 30 people."
Cdr Peter Stevens of the Met Police said his thoughts and sincere sympathies were with the family of the man who was killed and the people who were injured.
He said officers were working hard to establish exactly what happened, adding that nobody else was being sought in relation to the attack.
Police tape continued to surround the market area on Monday, with debris scattered across the road.