A teenager was arrested in the UK on Wednesday (local time) for allegedly fatally stabbing a girl from another school.
The Telegraph reported the 17-year-old boy allegedly stabbed her after she rejected flowers from him.
Police are yet to publicly identify the 15-year-old victim, who was killed on her way to class on a busy road in the south London town of Croydon during Wednesday's morning rush hour.
Tributes describe her as "very comedic" and "much loved".
Her school, the private Old Palace of John Whitgift, confirmed she was a student there, adding staff are shocked by her "senseless and tragic death".
"It will take some time for the Old Palace community to come to terms with this terrible news, and we will offer support to our pupils as we try to do so," a statement from the school said, as reported by ITV News.
Anthony King, chairman of youth project My Ends, told the broadcaster the girl's family is "heartbroken".
"She had a bright future ahead of her."
Flowers and cards now line the pavement of the scene, local media said.
A witness told ITV blood was running "like water" as members of the public rushed to help following the attack.
Others claimed the stabbing happened after an altercation on a bus between the girl, her friends and students from another school.
"We were thinking, what the hell happened, maybe it was just a little fight or something?" one witness told ITV.
Chief Supt Andy Brittain, of London's Metropolitan Police, said it's every parent's worst nightmare.
"I know the officers who responded this morning, along with our emergency service colleagues, are devastated at the victim's death.
"This is an emotion I share and I know people across Croydon will be feeling the same," Brittain said.
London Mayor Sadiq Khan said he was "absolutely heartbroken" at the news of the girl's death.
A police investigation is continuing.
