A 19-year-old man has been killed and an 18-year-old critically injured in a shooting in Milton Keynes.
The incident happened in Fishermead Boulevard just after 2200 BST on Thursday.
Police said the 18-year-old had been shot in the head and was under an armed guard in Milton Keynes General Hospital "for his own protection".
It is believed the two victims were friends, but police do not know if the offender was known to them.
Det Supt Rob Mason said: "We are obviously still at a very early stage of this investigation.
"I realise that there is a lot of concern in the community as well as a lot of speculation about the reasons behind this incident.
"We are still trying to establish the facts and cannot be drawn on rumours and speculation.
"We have a large and highly visible police presence in the area which should provide some reassurance to the community at this difficult time.
"I continue to urge anyone who has any information about this incident to contact police urgently."
A large area of the estate has been sealed off while investigations are carried out.
Charity Crimestoppers is offering up to £5,000 reward for information leading to the arrest and conviction of those responsible for the shooting.