A second person has been arrested on suspicion of murdering teenager Jodie Chesney, who was stabbed in the back as she socialised with friends in a park.
Scotland Yard said a 17-year-old boy is in custody after being arrested in London on Friday morning.
Jodie, 17, was in the park in Harold Hill, east London, when she was approached by two males and knifed from behind in a seemingly motiveless attack on 1 March.
She was pronounced dead just over an hour after officers were called to what police described as a “savage, evil attack” at about 9.25pm.
A 20-year-old man arrested in Leicester on Tuesday evening remains in custody on suspicion of murder in London, police said.
Jodie was playing music with five other teenagers in the park when they became aware of two males who left at around 9pm without interacting with them, the Metropolitan Police said.
About 30 minutes later, the pair returned and one stabbed Jodie in the back without saying a word, officers added.
Calling for anyone with information to come forward, Detective Chief Inspector Dave Whellams said: “This was a savage, evil attack.
“At this time, there being no clear motive is very unusual. We retain an open mind and can’t rule anything out.”
Jodie’s death has added to the urgency for action to be taken to tackle knife crime across the UK.
Police have called for a reverse in the cuts to the number of officers under austerity measures, but Chancellor Philip Hammond on Thursday told forces to refocus their existing resources.
Jodie’s family have made an emotional appeal for help in catching the A-level student’s killer.
Father Peter Chesney said: “You can’t get kudos for stabbing a 17-year-old in the back. So, just dob them in, grass them up, this is not alright.
“It was obviously a murder as well, it wasn’t an accident... it was so ferocious the attack. She lost so much blood. This was on purpose, someone meant to murder her.”
A post-mortem examination gave the cause of the Girl Scout’s death as trauma and haemorrhage.
On Remembrance Day last year, Jodie posted to Instagram a picture with fellow Scouts at 10 Downing Street, and added the caption: “I’m basically famous now... this was such a good opportunity and so much fun.”