Two men now remain in custody on suspicion of murder after two teenagers were shot dead as they were chased down an alleyway.
Mohammed Abdi Farah, 19, died at the scene, and 18-year-old Amin Ahmed Ismail died after being taken to Milton Keynes Hospital in Buckinghamshire with a gunshot wound to the head.
The detained men, aged 33 and 21, from the Bletchley area, were arrested last night by armed officers from Thames Valley Police.
A 13-year-old boy, also arrested last night, has been released on police bail until the middle of June, a spokesman said.
The shooting happened on the Fishermead council estate in Milton Keynes, Buckinghamshire, shortly after 10pm on Thursday.
Both victims, who were from the Somali community, were known to police for low-level incidents and detectives have ruled out the killings being gang-related at this stage.
Mr Farah's uncle, Rashid Hirad, told Sky News that his nephew had been in hiding for the last few weeks.
He said Mr Farah had been beaten up repeatedly and his mother had moved to Birmingham in an attempt to avoid the trouble but he kept returning to Milton Keynes to visit friends.
Mr Hirad said: "She decided to move from Milton Keynes to Birmingham because she wanted to run away from these people but she couldn't. All the time he is coming back to Milton Keynes to visit friends and at last it happened."
Detective Superintendent Rob Mason, who is leading the investigation, said: "We believe that the victims in this incident are friends, but we do not know if the offender is known to them.
"I would ask that anyone who has any information about this incident contacts Thames Valley Police urgently."
Police have place two videos, one in English and one in Somali, on YouTube to appeal for witnesses to the shooting.