Two teenage boys were stabbed to death on Saturday night following a "shocking" altercation on a quiet housing estate in Milton Keynes.
One of the two 17-year-olds, who have not yet been identified, died at the scene while the other was taken to hospital but died in the early hours of Sunday, police said.
A neighbour who know the victims suggested the stabbing was related to a house party which had been held in the vicinity.
What appeared to be blood was smeared across the front door of a house in Archford Croft in Emerson Valley, Milton Keynes.
Two forensic officers could be seen inspecting an object on the driveway next to a black BMW.
Two males were also injured in the incident and were taken to hospital.
Thames Valley Police said they had suffered "serious, but not life threatening injuries".
One neighbour said she heard a "commotion" involving screaming shortly before midnight but did not see what happened.
"The police were here pretty quick," she said
Another neighbour, who lives in an adjacent cul-de-sac, said that she know the boys but declined to give their names.
She said: "This gang of kids have been hanging around Archford Croft - it's all gang-related.
"We do know that there was a house party at the time, not here but another part of Emerson. I think it's just because there was a house party and then the trouble started from there."
She said of the two boys: "I think they were friends but that's all we know. It's just because our kids all go to the same school together."
Her son said: "It's all drug-related, drug-related isn't it? All that stuff."
Another woman who lives opposite the cul-de-sac said she heard: "A little bit of music last night but that's it."
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Another neighbour said he had seen an altercation wand was being treated as a witness by police.
One woman, whose home overlooks the property's garden, said she did no see or hear anything and described the neighbourhood as "peaceful".
"It's just a nice peaceful part of Milton Keynes. There's never been any incidents, not since I've been here which is quite a while now," she said.
Detective chief superintendent Ian Hunter said: "Thames Valley Police is in the early stages of a double murder investigation after two teenage boys have tragically died in this shocking incident.
"Our priorities at this time are to conduct a thorough investigation and to support those who have been affected. Officers are currently at the scene which has been cordoned off and members of the public are asked to avoid the area.
"I would like to speak to anyone who has any information which could help with our inquiries or anyone who witnessed any suspicious activity in the area of Archford Croft at around the time of the incident around midnight.
"Even if you think details may be insignificant, please come forward and speak to police."
Knife crime has continued to plague the UK - with figures revealing it has risen by seven per cent in a year to hit an all-time high.
Police recorded 44,076 incidents involving knives or sharp instruments in England and Wales in the 12 months to June.
Almost half of these were stabbings while 43 per cent were robberies.
The total does not include figures from Greater Manchester Police — the UK’s third largest force — which records data differently.
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