Focus: Were the deaths of four people triggered by a man being refused a drink?

In Nottingham, a thousand mourners attended the funeral of Jamie Gunn, 19. Miles away, a village in Lincolnshire was coming to terms with the murders of Joan and John Stirland, who were shot dead in their seaside bungalow. The crime writer Brian Cathcart uncovers links between the deaths

For a 19-year-old described in the press as a doorman, James Gunn was unusually popular and well-connected - at least, if his funeral was anything to go by. Some 700 people crushed into the hilltop parish church of St Mary in Bulwell, Nottingham, for the service on Friday. Another 300 stood in the drizzle outside. A horse-drawn, glass-sided hearse waited at the gate below, alongside two motor hearses bearing flowers, including huge wreaths saying "Jamie", "Brother" and "Jim Bob".

Ready to convey leading mourners to the cemetery were three of the most stretched kind of stretched limousine, plus three big funeral Daimlers, a convoy of bulky, dark 4x4s and a conspicuous black Mercedes two-seater.

Hard-looking men with stubble for hair stood smoking and chatting quietly in the churchyard, their jackets straining across the shoulders. The style as well as the scale of the funeral would have suited a Kray brother, rather than a teenage bouncer unknown to the world outside Nottingham before his death.

Gunn died of pneumonia at his family's home in Bestwood, a district bordering Bulwell. His mother told the Nottingham Evening Post that it was the end of a terrible year in which her son had surrendered to drink, illness and despair.

Tragic enough in itself, his death may also be pivotal to something bigger and much more sinister: a chain of events that appears to have claimed four innocent lives, put one man behind bars until 2028 and chased another into long-term hiding. Still more people are now under police protection.

Among the casualties, it seems, are Joan and John Stirland, the middle-aged couple shot dead last weekend in the tiny Lincolnshire seaside resort of Trusthorpe.

As Jamie Gunn's long funeral cortege edged away at walking pace from St Mary's Church on Friday, just a mile away on Hucknall Road a demolition team was tearing down the last recognisable traces of a big pub called The Sporting Chance. The coincidence of funeral and destruction was a fitting one, for it was at The Sporting Chance, in the dark hours of a Saturday morning one year ago, that the terrible chain of events began.

There was a "lock-in" that night - customers were inside having a late drink - and at the door, a young man was refused admission. Michael "JJ" O'Brien, 22, had already been turned away from two bars because he was wearing trainers and a tracksuit top.

A scuffle took place and O'Brien was hit on the face, possibly with an ashtray. He was with his friend Gary Salmon, 31, and the two retreated to Salmon's flat nearby, where they changed into dark clothes, gloves and balaclavas. They also picked up a single-barrelled shotgun.

Back at the Sporting Chance, four men left the pub and got into a Renault Laguna car. At the wheel was Marvyn Bradshaw, 22, a shopfitter who lived locally and who had no involvement in crime. Beside him sat his longtime friend Jamie Gunn. His family were well known in Nottingham, including to the police.

As the car edged out of the car park, a shot was fired and Bradshaw, hit in the head, slumped sideways. He died later in hospital. Bradshaw had almost certainly been shot by mistake. Neither he nor Gunn is believed to have been the person who struck out with the ashtray in the first place.

O'Brien, a small-time drugs dealer who had served time in jail before, was arrested within days and stood trial for murder last month at Nottingham Crown Court.

Thanks to the courageous testimony of two teenage girls who were in Salmon's flat that night - one heard O'Brien say: "I shot him; he was a bad man" - he was convicted. Police are still looking for Salmon, who disappeared immediately after the murder.

The shooting was the 17th to take place in the city that August, and as unrelated manhunts north of the city this weekend bear witness, the murders continue. But there is more to the Bradshaw case. The Gunns struggled to cope with Jamie's reaction to the death of his friend Marvyn.

"It was indescribable," his mother Julie said. "He was screaming and crying. He just couldn't believe it."

A steep decline had begun. "Jamie held Marvyn in his arms after he had been shot. I think he may as well have died then too," she said.

O'Brien also had a family, whose members felt the consequences of these events: his mother Joan, 53, was a nurse and she was married to John Stirland, 55, who worked in a textile factory.

How much contact they had with her violent son is not clear, but he was not living with them.

Three days after O'Brien's arrest for the Bradshaw shooting, just after 10pm on a Sunday evening, shots were fired through the windows of the Stirland's home in the northwest of Nottingham, possibly by two men who were seen on a motorcycle. Terrified and believing their lives to be in danger, the couple informed the police and moved out that same night.

They changed address several times over the next few months before renting a seaside bungalow 80 miles away in the part of Trusthorpe village known as Radio St Peter because it once housed a big transmission mast. If Joan Stirland thought of herself as being in hiding in Trusthorpe it must have been in a limited sense, for she told several acquaintances in Nottingham that she had moved to the coast. It seems likely that she felt 80 miles and a reasonably low profile were sufficient precautions. She had done nothing wrong, after all, and her son was in custody awaiting justice. When did anyone last attempt to take revenge on the innocent relatives of a killer?

O'Brien was convicted of murder just under five weeks ago, on 12 July. His reaction in court was extraordinary: when the judge declared that the guilty man should serve no less than 24 years - more years than he has been alive - he made light of it: "I will do that standing on my head," he said. "I'm a bad boy, I don't care."

O'Brien also threw a glass of water towards the parents of his victim and taunted them: "Your son looked like a doughnut with a big hole in his head."

The conviction brought only passing comfort to Jamie Gunn, according to his stepfather, David Sheffield. "He was glad that justice had been done, but he went back to thinking about Marvyn again. He had the vision of that night in his head." Three weeks after the trial, on 2 August, Gunn was found dead in his mother's bed by a younger brother and sister. Five days later, at about 10.30pm on Saturday, 7 August, a neighbour of the Stirland's in Radio St Peter noticed a man lurking by their front door.

She did not report it immediately but spoke to Mrs Stirland the next morning. Joan was concerned enough to ring the Nottinghamshire police who she had stayed in touch with ever since the shooting. Shortly before 2pm that Sunday an officer called her back to discuss things.

The police insist that Mrs Stirland was concerned but not panicked, that her priority was to inform them and that she put the emphasis on discretion.

She did not want police cars swooping on the house and alarming her neighbours. The Nottingham officer passed this message on to his Lincolnshire colleagues.

Again, these responses were probably normal. That a blameless couple in their fifties might be in danger because of something that they had no involvement in, and which their son had already been punished for, still seems an outlandish notion. What would be interesting to know, however, is whether Joan Stirland or the Nottingham police officer she spoke to were aware last Sunday that James Gunn had died, and whether this was mentioned between them. The police are not saying.

Minutes after Joan put down the phone, a black Volkswagen Passat pulled up outside her bungalow and two men wearing boiler suits and baseball caps got out, leaving the hazard lights flashing. Very soon, they emerged again and drove off, leaving the door to the bungalow ajar. The Stirlands were inside the house, dead from gunshot wounds.

The Passat was found burning in a quiet country lane two miles away, presumably set alight after the killers had switched cars. Police were later able to reveal that it had been stolen on 31 July - in Nottinghamshire. The Lincolnshire police force, on whose patch the murders occurred, are leading the investigation.

For Nottinghamshire police, who currently have 13 major investigations under way, that is probably a relief. But the respite will probably be short, for it appears that all the roads in this case lead back to Nottingham.

Friends and associates of Jamie Gunn may head the suspect list, although the police refuse to confirm this. There was talk of officers mingling with the crowd at Jamie Gunn's funeral, in the expectation that the killers might be there.

But mingling would have been difficult for anyone not known by the family. And aside from the 1,000 people at the funeral, last week the In Memoriam column of the Nottingham Evening Post carried around 30 messages mourning the 19-year-old every day.

The list of people who feel deeply about the loss of Jamie Gunn is not short. The police inquiry into the murders of John and Joan Stirland, who are also mourned, may take quite some time.

Brian Cathcart is the author of books on the murders of Jill Dando and Stephen Lawrence