Video report by ITV News Correspondent Neil Connery
The uncle of 17-year-old Jodie Chesney, who was stabbed to death in a London park, has paid tribute to his "beautiful, lovely and quirky" niece.
Metropolitan Police were called to reports of a knife attack in Harold Hill, Romford, around 9.25pm on Friday - with Ms Chesney dying about an hour later at the scene.
In a family statement given to ITV News, Dave Chesney said: "As you can imagine, we are all devastated.
"This was a totally random and unprovoked attack on a beautiful, lovely and quirky young girl with her whole life in front of her."
His comments follow a call from the teenager's grandmother, Debbie Chesney, to end the "needless violence".
On Sunday, Scotland Yard shed further light on the attack, saying that Jodie had been with a group of five teenagers playing music and socialising in the park on Friday evening.
"Jodie's group were aware of two males in the park who left at around 2100hrs without interacting with Jodie or her friends," a police statement read.
"Around 30 minutes later the pair returned to the park and walked straight towards the group, where one of the males stabbed Jodie once in the back.
"Nothing was said by the two suspects, who ran off in the direction of Retford Road.
"The suspect who attacked Jodie is described as a black male aged in his late teens. There is no further description of him at this stage, nor is there any description of the other male."
Friends of Ms Chesney paid tribute to her and told ITV News how she was always "laughing" and "smiling".
A mother-of-three who tried to help the teenage girl in the park was "shocked by the amount of blood", her husband said.
Paul Farenden, 54, said his 49-year-old wife Teresa had rushed to the scene near their home to see if she could help after she heard screaming.
He added: "My wife asked if everything was alright and one of the boys said 'no, my girlfriend has been stabbed'.
"She put her in the recovery position and waited for the ambulance to turn up. I think she tried to resuscitate her.
"She thought it was all over then and it would be alright."
Police said that no arrests have been made so far.
DCI Dave Whellams said: "I am appealing for any witnesses who have yet to speak with police to call me.
"There has been excellent support from the local community and a number of people have shared information with police, but there will be other witnesses and people with information that may prove crucial.
"Although the description of the suspect is limited, I am certain that people will have seen the two males hanging around the park or running away from the scene - or will otherwise have noticed something suspicious. I need those people to call me."
Police are urging anyone with information to contact the incident room on 020 8345 3775, tweet @MetCC or call Crimestoppers anonymously on 0800 555 111.