The policeman leading the investigation into the north London stabbings that left a man dead has said he did not know what motivated the attacker.
Ch Supt Simon O'Brien is leading the investigation
Enfield Borough Commander Ch Supt Simon O'Brien also described how some of the six victims "carried on" not realising they had been stabbed.
Detectives have contacted local mental health trusts to check the arrested man's name against their records.
Mr O'Brien said the victims were "completely random".
Hundreds of police officers are now working on the case.
Mr O'Brien said: "It's very difficult to know what prompted this.
"The first victim was a man who was walking to the station to go to work. He had just left his girlfriend when he was stabbed a couple of times in the back.
"He thought he had been punched and carried on.
"The calls then started coming in thick and fast and we realised we were probably dealing with the same guy stabbing people."
A man is being held in connection with the attacks
He said the spate of stabbings had been classified as a "super critical" incident.
He said: "It was a very dynamic situation and it was very difficult to know where the next one was going to happen or what was going to happen in the next few minutes.
"(The attacker) was coming out of the vehicle, picking people at random, male and female. Some were cycling, some were walking and he stabbed them before getting back into his car.
"It's horrendous and I don't know what the motivation is."
He said victims had been stabbed one or two times each.
"Some of them carried on walking thinking they had been punched," he said.
"One of the victims was a woman cyclist who thought she had been punched and carried on cycling.
"Finally we got a few calls with registration numbers for the car and we went to an address.
Trail of blood
"Officers had just turned up when the suspect arrived in his car."
The suspect was arrested by unarmed officers and had blood on his clothes and inside the car.
The final victim discovered was a man in his 70s who walked into hospital having been stabbed.