A man on a motorcycle has been shot dead on a motorway in Warwickshire - and police are appealing for witnesses as they launch a murder inquiry.
The man was travelling south on the M40, between junctions 13 and 12 near Leamington Spa, when the incident happened at 1420 BST.
West Midlands Ambulance said they found the man with serious injuries, but he died at the scene.
It is thought the victim might have attended a biker party earlier.
"Road rage is not a line of inquiry. We are treating this as murder," said a police spokesperson.
It is thought the victim may have been at the Bulldog Bash, billed as Europe's top biker party, held at Long Marston airfield near Stratford.
Fingertip search
Motorbike gang links are a "strong line of inquiry", said a police spokesperson.
The incident caused 10-mile tailbacks in both directions - and police and the Red Cross are believed to be bringing food and water to drivers caught in the crime scene.
BBC reporter Liz Copper, who was at the scene, said it was understood a fingertip search of part of the carriageway would be carried out.
Paul Roberts, from Worthing, was driving along the M40 when the incident happened.
He said: "Suddenly we had to stop... soon other motorists were out of their cars and on the carriageway.
"One lady in a BMW took a first aid kit to the man who was lying on his front just next to the central reservation.
"It was very noticeable that the man was very still and was not wearing any shoes."
Police are appealing for any motorists travelling on the M40 who may have witnessed the incident to contact them.
An incident room has been set up at Warwickshire Police headquarters.
Weird how come he wasnt wearing any shoes???
Biker shot Dead
Moderator: Staff
Well seems like its been confirmed he was an hells angel god help the person who did it i wouldnt want to be in his shoesThe M40 in Warwickshire remains closed as police hunt the killer of a Hells Angel shot dead as he rode home from a motorcycle festival.
The victim, believed to be a Hells Angel in his 30s, was travelling south with two friends after attending the Bulldog Bash biker festival near Stratford when the incident occurred between junctions 13 and 12 shortly after 2.15pm on Sunday.
The M40 will be shut southbound between junctions 15 and 12, and northbound between junctions 12 and 14, until around 4pm, police saidA post-mortem examination on the body has revealed he died from a single gunshot wound to the head. Warwickshire Police said they believed the fatal shot had been fired from a handgun.
Hundreds of cars were stuck on the motorway when the area was sealed off. Police want to speak to the driver and occupants of a green Rover 620, seen travelling south close to a group of motorcyclists at around the time of the incident.
The cars stuck earlier have all been allowed off the motorway but the Highways Agency said the stretch of the M40 past the murder scene is likely to be closed "at least until early in the morning".
Detective Superintendent Ken Lawrence of Warwickshire Police said: "I'm still interested to traced a Rover 620 motorcar...described by some witness as being beside or very close to the motorcyclist at the time."
A post-mortem examination will be carried out later on the victim who has not been formally identified.
Bulldog Bash organiser, 56-year-old Hells Angel "Bilbo", said: "I knew the lad and you couldn't wish to meet a better person. We are used to deaths as bikers because people die in accidents. But we don't expect someone to get shot."
The event, which is not being linked to the killing, is billed at Europe's number one biker party and attracts tens of thousands of motorcyclists and music fans from across Europe. This year Status Quo headlined the event.
"Bilbo" continued: "This is murder plain and simple and we have no idea why this happened. We're just devastated. It's dangerous to guess why (this happened). This year was a massive event and it went off virtually trouble-free.
"We had an amazing weekend and then this happened and it has totally shaken everybody. It's a massive loss to the biker community as a whole."
The shooting echoes a strikingly similar incident six years ago when three bikers were shot at on the M40 as they returned from the Bulldog Bash. At the time police said it was an "indiscriminate" attack.
The bikers, from Canada and France, were travelling in the inside lane towards Oxford when they were shot at from a car in the middle lane. A 31-year-old man was hit in the right leg and taken to hospital for treatment.
Motorists are being advised to take alternative forms of transport while the M40 motorway remains closed or use the M1 or M6.