The mother of a six-year-old boy was one of two victims murdered in separate killings less than a mile apart in north London.
The other victim, a 24-year-old man, was killed in a drive-by shooting at point blank range.
Detectives from the Metropolitan Police murder squad are investigating the deaths, the first of which took place in Belmont Street, Camden.
A woman in her early 20s, named locally as Shakira, was stabbed at around 11.15pm on Sunday and, despite treatment from paramedics, was pronounced dead at the scene just before midnight.
A trail of blood could be seen on the ground near the scene of her death on Monday.
Terry Ellis, from the Camden Against Violence, said the stabbing victim regularly attended the group’s events.
“She’s a mother, she’s got a six-year-old kid,” he said. “As far as I know it was an argument she wasn’t really involved in.
“She was just in the wrong place at the wrong time. It wasn’t gang-related, it wasn’t drug-related.
“She was a wonderful young lady, always happy. She’s got a lovely son and was just a normal mother.”
Mr Ellis said the family of the young mother have been left “devastated” by the killing.
“She’s just a normal mum,” he added.
Two other women suffered slash wounds. Scotland Yard said a 35-year-old woman has been arrested on suspicion of murder.
Friends of the victim left floral tributes at the scene on Monday.
One, who gave her name as Ronney, 21, described her as a “really, really good mum”, who “adored” her son.
“She was part of everyone’s life, she helped everyone,” she said. “She was part of my family. She was lovely.”
The woman, who said she used to live with the victim, said she was not involved in an argument that broke out, but was sticking up for someone else.
“I don’t know why people feel the need to carry knives. People just don’t think before they do things,” she added.
The second killing saw the 24-year-old man shot dead about half a mile away in Malden Road, Kentish Town, just before midnight on Sunday.
He was shot “at close range” after being approached by a moped rider who was carrying a passenger, according to Detective Chief Inspector Simon Stancombe, from the Metropolitan Police’s Specialist Crime Command.
He added: “Everything we have found out so far points to this being a drive-by shooting.”
Mr Stancombe appealed for witnesses to come forward, adding that a Toyota Prius, Ford Focus and motorbike seen in the area at the time were of particular interest to police.
A 25-year-old who gave his name as Will described how he battled to save the man’s life as he lay on the ground with a gunshot wound to his chest.
“We heard a gunshot, what we thought was a car backfiring, maybe a firework,” he said.
“We saw a man moving, there wasn’t anyone around him.
“By the time I got there, there was a group around him.”
The teaching assistant continued: “No-one was doing anything to the body so I did first aid, CPR, while I was on the phone to the ambulance.”
Will said another bystander used a jumper to plug the gunshot wound in the victim’s chest.
“It was unclear whether he had been shot in the front or the back and it was a large wound,” he said.
“By the time they (medics) turned up I did about three rounds of CPR and they operated on him immediately but I think he was unsaveable.”
A father-of-three, who works nearby, said he was “shocked” after hearing a single gunshot.
“I was working here and I heard a bang,” the 42-year-old said.
“It was really loud. I have never had anything that close, in terms of shooting, in my life.”
He continued: “Then I just went back to work as normal and then I saw some people running, panicking and I went and saw him lying there. I saw him lying on the street.”
The man, who did not want to be named, said police and paramedics arrived on the scene around 10 minutes later.
“Some people were helping him. Some people stayed but because they were young boys they were a little bit scared.
“Then a couple of people stopped driving, they were more mature, and started to press the heart and give CPR.”
An air ambulance was sent to the scene but the victim was pronounced dead shortly after midnight.
There is no link between the two north London deaths.
The violence came after Camden Against Violence ran a series of community events over the weekend.
“We woke up this morning and it’s been marred by two tragic deaths. Our hearts go out to the families. We are still in shock,” he said.
The man who died in Kentish Town was the second person to die of gunshot wounds in the capital in less than 12 hours.
At 3.45pm on Sunday, firearms officers were summoned after shots were heard in Sydenham Road, south-east London.
The victim, who was in his 20s, died at the scene at 3.50pm, police said.
Witnesses in the area told the PA news agency that they had heard reports the man had accidentally shot himself.