Witnesses to a multiple stabbing in a Sainsbury's car park have said the attacker "appeared out of it", adding that he "only went for women".
Four women were stabbed in the chest, legs and back at the Hampton supermarket in south-west London.
One of the women was taken by air ambulance to hospital where she is being treated for life-threatening injuries.
A man in his 60s was arrested at the scene on suspicion of attempted murder and is being held in a nearby police station.
A female eyewitness, who did not want to be identified, said: "The attacker only went for the women.
"The man ran through and started attacking them. It didn't seem like they knew him it was completely unprovoked.
"One lady is in very bad condition, she had to be air-ambulanced out."
If the attack had occurred "10 or 20 minutes" earlier, there would have been children present as a primary school is right next to the car park, she said.
The woman, who did not want to be identified, added: "He appeared to be out of it, on drugs or crazy. He must have been very angry to go out and unprovokedly stab those women.
"The woman who was badly stabbed in the back made it up to the police station and raised the alarm.
"She is well-known locally and always goes shopping there all the time."
A spokesperson for the Metropolitan Police has said the attack is believed to be terror-related.
