A man may have been shot simply for bumping into a gunman, police said.
Police said the area does not have a problem with gun crime
The victim is still critically ill in hospital after being fired at in Upper Street, Islington, north London, on Wednesday evening.
Police are still trying to work out if the person who shot a woman inside Finsbury Park Tube station about 30 minutes later is the same hooded man.
She was hit as she stood near two men who the gunman is thought to have been aiming at. She was not seriously hurt.
The woman, aged in her 20s, was shot in the back. She was taken to hospital but has since been discharged.
The first attack took place at about 1845 BST on Wednesday and the gunman was chased by one of the victim's friends
Eyewitness Katherine Roberts told BBC London: "It was absolutely terrifying. I heard a gun shot and saw a man brandishing a pistol.
"He was running up the road firing behind him. People were spilling out onto the street.
"I actually crouched down behind a wall because I thought it was the safest place to be."
Det Ch Insp Penny Banham said: "The suspect shot the victim basically for banging into him in the street, which is just totally unprovoked and random."
Chief Superintendent Barry Norman said: "It's one of the worst things that has happened here in the last three years.
"This is not a borough that suffers a lot of gun crime in spite of us being an inner London borough - so we are all shocked."
In both cases, police have described the suspect as a white man wearing a grey hooded top.
Parts of Upper Street in Islington were cordoned off but reopened on Thursday afternoon.