Tributes have been paid to a "kind and thoughtful" seven-year-old girl who died after she was found seriously injured on a playing field.
Katie Rough was found down a track after police were called to an address in the Woodthorpe area of York on Monday.
She was taken to hospital but died a short time later, North Yorkshire Police said.
A 15-year-old girl was arrested and remains in police custody.
Tracey Ralph, headteacher of Westfield Primary School where Katie was a pupil, said: "Katie was a kind and thoughtful child who was well liked by both pupils and staff.
"She was hard working and showed a particular talent for creative writing.
"Her death is a terrible loss which has deeply saddened our school community and we send our profound sympathies to her family.
"All members of our school are being offered emotional support at this distressing time."
Jon Stonehouse, director of children's services at City of York Council, said the "tragic incident" had "shocked the city" and specialist support was being offered to the school and wider community.
Witnesses described how Katie's mother, named locally as Alison Rough, fell to her knees in the street, crying and pleading for help after her daughter was injured.
Residents living in Alness Drive said Mrs Rough asked them to call an ambulance for Katie, saying "I think she's killed her".
Rob McCartney, 50, said he saw the young girl lying in the field near the quiet cul-de-sac and her mother running up the street "shouting for help".
"(The mother) was back and forth, obviously very, very distraught and who I think was the father turned up.
"I spoke to her later, asked if she was OK and she said 'No, no, she's my little girl'.
"She said, 'I think she's killed her'."
A woman living in a house by a track leading to the playing field said: "The mother was on her knees in the middle of the road, crying and saying things."
Neighbours said children often used the playing field during the summer and it was popular with dog walkers.
The area was cordoned off on Tuesday while forensic officers examined the scene and mourners arrived throughout the day to lay flowers in the street.
One couple, believed to be the young girl's grandparents, left a bouquet with a card, which read: "Night, night my darling princess Katie, love Nana and Grandad."
At the family's home, just less than a mile away from the scene, two police vans were parked outside and an officer was seen entering and leaving the property carrying equipment.
Police have appealed for anyone who may have seen the two girls in the area of Morrell Court, Bellhouse Way, Osprey Close and Alness Drive between 3pm and 5pm on Monday to get in touch.
A force spokesman said the investigation into Katie's death was ongoing, adding: "Katie's family are devastated by this tragic event and have asked for their privacy to be respected at this extremely distressing time."
Anyone with information that could assist the investigation should call 101, select option one, speak to the Force Control Room and ask to be put through to the Cleveland and North Yorkshire Major Investigation Team using the reference number 12170004685.