A 17-year-old boy has been stabbed to death in High Wycombe, Buckinghamshire in a “targeted attack”.
A second 17-year-old boy was also hurt in the Sunday evening attack but his injuries are not thought to be life-threatening.
Police are searching for four suspects, who all had their faces covered at the time.
No arrests have been made.
Detective Superintendent Kevin Brown, of Thames Valley Police, said: “We are in the very early stages of this investigation and details as to what has happened are currently very limited.
“The incident occurred between around 7pm and 7.30pm close to the main car parks of Easton Street at a time when members of the public would have been using the car parks, attending the theatre or preparing for a night out in the town.
“It is therefore very important that anyone who was close to Easton Street at this time and saw something unusual or out of the ordinary or indeed knows anything about this incident gets in touch as soon as possible.”
He added: “This is a tragic incident in which a teenage boy has been killed, and I know that it will cause a great deal of concern in the community.
“However, I’d like to reassure everyone that we are carrying out a thorough investigation into what appears to be a targeted attack.”