Police are continuing to question four men arrested on suspicion of murder after a man died soon after armed officers stopped a van in Berkshire.
The man died in London Road, Sunningdale, near Ascot, after being found inside the van which was stopped by officers on Wednesday afternoon.
Four other men inside the van, who attempted to escape, were arrested.
Thames Valley Police said officers had been looking for the vehicle after receiving a tip off.
The van was stopped by police at about 1400 GMT.
Witnesses told the BBC police appeared to hold the arrested men at gunpoint for more than 45 minutes before discovering the victim's body was in the van. They said it was contained in a "white cement sack".
They said the man's body was then covered by a large blue tarpaulin, next to a white Mercedes Sprinter van.
Supt Richard Humphrey, of Thames Valley Police, said no shots were fired during the incident and the injured man was only found when a thorough search of the van had been carried out.
He said: "There were four occupants in the vehicle who attempted to run off. Three were detained in the immediate vicinity of the van and the fourth was arrested after a more extensive search.
"The officers returned to the van that had been stopped and then made a search of the vehicle.
"They found a seriously injured man within and immediately commenced first aid and called an ambulance.
"Despite the efforts of the officers and of the paramedics this man has now died."