Evil farm labourer John William Cooper has been jailed for life without hope of parole after a jury convicted him of four horrific murders.
Cooper, 66, was also found guilty of raping a 16 year old girl and sexually assaulting her friend.
The gunman who terrorised the quiet county of Pembrokeshire will now be investigated for three more mysterious deaths.
Cooper robbed, burgled, raped and murdered his way across the countryside with a balaclava in his pocket and a sawn off shotgun strapped to his back and hidden under a coat.
He blasted to death holidaymakers Peter and Gwenda Dixon, aged 51 and 52, as they enjoyed a last walk along the Pembrokeshire Coastal Path in June, 1989 "for a pitiful amount of money".
The Dixons had spent every summer holiday walking the path
Four years earlier he had shot to death millionaire farmer Richard Thomas, 58, and his sister Helen, 56, after they caught him breaking into their home at Scoveston Park near Milford Haven.
And in 1996 he held up a group of five teenagers at gun point as they played in a field, raping one, indecently assaulting another and trying to rob all five. Police believe he was looking for more burglary targets at the time.
Cooper, of Spring Gardens, Letterston, near Milford Haven, was arrested in 1998 and jailed for 16 years for 30 burglaries and the violent robbery of retired schoolteacher Sheila Clark in her home in the village of Sardis.
Police kept thousands of items found during Operation Huntsman, including a sawn off double barrel shotgun thrown away in a hedge near Cooper's then home in Jordanston.
In 2007 a cold case review was launched and experts using modern forensic techniques began to find links between Cooper, the murders and the sex attacks.
Cooper never took off his gloves--even while putting his hands down the knickers of the 15 year old girl--and never threw anything away.
Experts linked fibres from gloves found at his home and hidden in hedges nearby with all the crimes.
They also found a spot of marketing executive Peter Dixon's blood underneath paint on one of the barrels of the gun, which Cooper had thrown into a hedge as he fled from the robbery of Mrs Clark.
And a pair of shorts lying on top of a wardrobe in his bedroom displayed the DNA of the Dixons' daughter, Julie. Nineteen eighty nine was the first year she had not joined her parents, from Witney in Oxfordshire, on their summer walking holiday.
Cooper told the jury at Swansea crown court that he had worn the shorts to bed.
Police found a key that fitted a bedroom lock at a farm owned by Richard Thomas.
Cooper was released from his 16 year sentence in December 2009. But police were closing in again and just three months later he was arrested as he walked to a shop to buy a newspaper.
Today, Cooper, defiant to the end, continually interrupted Mr Justice John Griffith Williams as he handed down four life sentences and told Cooper that in his case "life will mean life."
Cooper shouted "rubbish" and accused the prosecution of witholding evidence from the jury as Mr Justice Williams described him as an evil and dangerous man who would never admit his guilt or show any remorse.
The foreman of the jury wiped tears from his eyes as Mr Justice Williams told Cooper, "Only you know the full facts and circumstances of the four murders. Much will never be known because you have constantly refused to stand up to your responsibilities.
"No doubt you wil continue to deny what you have done and you will never show remorse.
"You are a very dangerous man, a highly organised predatory burglar whose hallmarks were a balaclava, gloves and a shotgun.
"Each was well planned and you evaded arrest for so long. If not for the advances in forensic science you might well never have been brought to justice."
He added, "Helen Thomas must have been terrified. She had to die because she recognised you. There is a strong suspicion that you sexually interfered with her. It is likely her brother heard the shot."
Cooper shouted "utter rubbish" and that "what that jury was not told is going on the internet."
Mr Justice Williams threatened to send him to the cells but continued, saying that the Dixons must have been terrified as they faced execution, one having heard the other being shot dead and knowing they were about to suffer the same fate.
He said the Dixons had suffered "such evil wickedness" as they were executed in cold blood.
"Life for you will mean just that," added the judge.
Mr Justice Williams said it was academic but Cooper would serve 15 years for the rape, 8 years for the indecent assault and seven years for the attempted robberies.
He exused the jurors from serving again for the next 20 years.
Earlier, Gerard Elias QC, prosecuting, said the rape victim still had difficulty having sexual intercourse with her husband. "Her confidence has been knocked for life and she does not believe she will ever full recover," he added.
The girl, 15 in 1996, who was sexually assaulted could not stand to be touched by someone wearing gloves and a third girl in the group turned to alcohol and later died.
The two boys in the group were still haunted by Cooper's attack on them.
Mr Elias said that 22 years after the murder of her parents Julie Dixon, now Julie Pratley, could still not bring herself to walk anywhere near the coast.
He said both Peter and Gwenda Dixon had been busy in their local community around Witney, Oxfordshire, where Peter Dixon had held the rank of Squadron Leader for his work with the local RAF cadets. Gwenda Dixon had been secretary of her local badminton club.
Richard and Helen Thomas had been strong church goers.
Afterwards, the Dixons' son Timothy said he was "pleased" with the verdicts but an integral part of the family was missing.
"Mum and Dad were loving, gentle and loved people. Even after two decades their absence is immense and still painful."
Det Chief Superintendent Steve Wilkins, who led the investigation, said, "Following a court appearance in 2009 John William Cooper shouted to the communities of Wales not to judge him until the evidence had been heard.
"Over the last nine weeks 12 people from the community have listened to all of the evidence and decided he is guilty. I believe this is the right decision.
"Cooper is a very dangerous and evil man who, for pitiful gain, murdered four people and later subjected five children to a terrible attack. He will now spend the rest of his life in prison."