Two men have been arrested on suspicion of murder after a man in his 50s was found dead in the street.
Thames Valley Police said officers on patrol found the victim on the ground in Micklefield Road, High Wycombe, at the junction with Hicks Farm Rise, at about 00:20 BST on Saturday.
He was surrounded by a group of men, who fled the scene when the police arrived.
Officers have appealed for anyone with information or footage to contact them.
The force said officers who discovered the man found he was not breathing and tried to revive him.
Paramedics continued to give the victim CPR but the victim was declared dead at the scene.
His identity and his cause of death are yet to be confirmed.
Shortly after the victim was found, a 25-year-old man from High Wycombe was arrested.
On Saturday night, officers arrested a second man, aged 27, and also from the town.
Both were taken into police custody for questioning.
Det Supt Ailsa Kent said: "We would urge any of the males who were at the scene to contact the police as soon as possible, as they may have vital information that can assist our investigation.
"I appreciate that the news of this murder will shock the community, but please be reassured that Thames Valley Police is conducting a thorough investigation to establish what happened. Anyone with any concerns can speak to our officers at the scene.
"I thank the public for their understanding and support while we carry our investigation."