Three men have gone on trial charged with the murder of a bodybuilder.
Dave King, 32, of Stevenage, died in a hail of bullets fired from an AK47 as he left the Physical Limits gym in Hoddesdon, Luton Crown Court heard.
A jury was told he was "ruthlessly executed" in October 2003 after a contract was taken out on his life.
Roger Vincent, 33, of Penn, Bucks, David Smith, 33, of Elstree, Herts, and Jason Attridge, 36, from Broadfields, North Harrow, all deny murder.
A fourth man, Julian Elfes from High Wycombe, has pleaded not guilty to perverting the course of justice and assisting an offender.
Mr King's criminal associates thought he had become a "grass", the court heard.
He died almost instantly when a van pulled up beside him and a masked gunman began firing through the open window.
Prosecuting Andrew Bright QC said: "It was all the more surprising because it occurred in a sleepy Hertfordshire town and involved the use of a weapon more commonly associated with terrorist activity in Afghanistan."
The prosecutor said: "He was a man with a history of involvement in crime. He was not a man of unblemished character."
The jury heard Mr King had been friends with Mr Vincent and Mr Smith, and others in their circle.
"Mr King met his death because he had made enemies amongst his former associates, most very probably because he was thought to be a police or a customs and excise informer - a grass," Mr Bright said.
The court heard two masked men had been inside the van. "Vincent very probably was the one to fire the gun and Smith was probably the driver of the van," said Mr Bright.
Mr Attridge, although not present at the time of the killing, was part of the murder team and had provided one of the getaway cars, the prosecution said.
Mr Elfes' role, it said, was to help his friend Mr Vincent lie low after the murder at a hotel near Heathrow Airport and provide a false alibi.
The case continues.