A British teenager has been knifed to death on a crowded bus in an apparently random attack as she made her way to school.
Christina Edkins, 16, was killed shortly after she boarded the double decker during the morning rush hour.
Police launched a massive manhunt for a fellow passenger who fled the scene after her murder and later arrested a 22-year-old man after an extensive search involving police dogs and firearms officers.
The stabbing came a month after Christina voiced concerns about a fellow passenger on another bus journey.
On February 8 she told friends on Twitter: "This man is worrying me on the bus keeps getting up and walking up and down stairs, and sitting in different place."
The teenager was attacked in front of hordes of commuters in Birmingham about 7.30am on Thursday.
The bus driver raised the alarm but medics were unable to save her.
Christina is not believed to have known her assailant, who was already on the bus when she got on board.
Detective Superintendent Richard Baker said detectives were investigating the theory her murder was a random attack and officers were considering a number of possible motives.
Just hours earlier, the teenager had posted some apparently despairing messages on Twitter.
She wrote: "Why can't something go right for once" and her final tweet read: "Don't need anyone to talk to about how I feel just need someone to be lazy with me and watch films and make me laugh."
Police said they would consider her social networking footprint as part of their investigation.