But just a fortnight later, Katie was found with serious injuries near her home in the Woodthorpe area of York.
A 15-year-old girl has been arrested following the death of a child in northern England, police said on Tuesday.
Katie was taken to hospital shortly after police arrived at the scene but died soon after, the BBC reported.
A police cordon in place on a footpath leading from Alness Drive.
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'.
Head teacher Tracey Ralph has described her as a "kind and thoughtful child".
"Her death is a awful loss which has deeply saddened our school community and we send our profound sympathies to her family", said head teacher Tracey Ralph.
"All members of our school are being offered emotional support at this distressing time". Mourners arrived with flowers to pay their respects.
Teenager, 15, charged with murder of York girl, 7
She added: "I arrived in my auto behind the mother".
Neighbour Connor Sinclair, 41, said: 'Katie was a really sweet girl, she always looked happy.
Another neighbour described Katie as a 'quiet, shy and pleasant little girl'.
"The most crime we've had around here is someone stealing windscreen wipers".
Officers remain at the scene today as the investigation continues.
May responded: "I join (Corbyn) in expressing condolences to the family and friends of little Katie who died so tragically". "I have a six-year-old daughter of my own and this kind of thing is terrible".
A local resident, whose partner works for the NHS, said he was told by the nurse that treated the girl that she suffered two stab wounds.
"They were obviously very distraught".
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