A fourth person has been charged with the murder of two 17-year-olds who were stabbed at a house party.
Dom Ansah and Ben Gillham-Rice were attacked at a birthday party in Milton Keynes on 19 October.
Two males were also seriously injured in the attack in Archford Croft, Emerson Valley.
A 15-year-old boy, from Milton Keynes, has been charged with two counts of murder and two counts of attempted murder.
He is due to appear at Milton Keynes Magistrates' Court on Friday.
Charlie Chandler, 21, of Fitzwilliam Street, Bletchley, Earl Bevans, 22, of no fixed address, and a 16-year-old boy from Milton Keynes, have previously been charged with murder and attempted murder.
A 53-year-old man and a 40-year-old woman, also from the town, who were arrested on suspicion of assisting an offender have been released while inquiries continue.
A 27-year-old Milton Keynes man arrested on suspicion of conspiracy to murder has also been released while inquiries continue.