A BESOTTED stockman who 'executed' a mum-of-three with a bolt gun in front of her children has been jailed for a minimum of 20 years.John McFarlane dragged popular fitness instructor Mary Griffiths out of her bed, where she was sleeping with her young daughter, Hannah, ten, after smashing his way into her house with an axe and turning off the electricity.

A BESOTTED stockman who 'executed' a mum-of-three with a bolt gun in front of her children has been jailed for a minimum of 20 years.

John McFarlane dragged popular fitness instructor Mary Griffiths out of her bed, where she was sleeping with her young daughter, Hannah, ten, after smashing his way into her house with an axe and turning off the electricity.

The Old Bailey heard how the 40-year-old killer first tried to strangle Ms Griffiths and then pumped one round from a captive bolt gun - usually used to stun animals before they are slaughtered - into her shoulder before pushing her down two flights of stairs.

As Hannah and her oldest daughter Jessica, 13, fought to fend him off, McFarlane pursued blood-covered Ms Griffiths, 38, into the street outside her home in Bullrush Crescent, Bury St Edmunds, shortly before 3am on May 6 this year.

There he pinned her to the ground, knelt next to her and fired two more rounds into her chest in what one witness described as an 'execution' killing - as her horrified daughters looked on.

She died later in West Suffolk Hospital.

McFarlane, of Bockhill Road in Bury, had originally denied the murder but changed his plea to guilty at Ipswich Crown Court last Friday.

He was besotted with Ms Griffiths and, as his own marriage broke down, became enraged when she made up with her boyfriend.

McFarlane, who has a history of mental problems, took the bolt gun from the Denham Estate, where he worked as a stockman.

An hour-and-a-half before Ms Griffiths was killed, McFarlane left her a Facebook message which read: 'They say there is nothing worse than a woman scorned.

'Watch this space because if someone rips out your heart and stamps on it then they deserve the same.'

Indeed, Ms Griffiths had become so worried about his unrequited attentions that she called the police for advice- only to be murdered by him a few hours later.

In sentencing Mr Justice David Bean said: 'You armed yourself with a stun bolt gun which it seemed you had removed the previous morning from the slaughterhouse on the farm where you worked.

'You also took with you an axe which you used to smash into the home where your victim lived with her three daughters.

'You used the bolt gun to shoot your victim in the shoulder.

'There was then a struggle, witnessed by her daughter Hannah, during which you tried to strangle Ms Griffiths. She managed to escape into the street, but you caught her there, pinned her to the ground, and twice shot her in the chest.

'A neighbour who witnessed the killing from a window described it as 'clinical', 'deliberate' and 'like an execution'.

'In a text message sent shortly afterwards you wrote 'Well, no one saw this outcome did they? Well, it had crossed my mind a few times. You said it was good to get angry. I am so angry and hurt and Mary needs teaching a lesson that if she rips out my heart and stamps on it then I will …'

'The consequence is that three generations of Mary Griffiths' family have suffered a tragic and devastating loss.

Her children have been deprived of a loving and caring mother. Her parents have had to endure the appalling experience of attending the funeral of their own daughter.

'The weapon which you used to shoot MG was just as lethal as a firearm.

'Other aggravating factors which lead me to classify this murder as particularly serious are that you broke into Ms Griffiths' home at night, carried out a prolonged attack, involving one shot in the house followed by two in the street, killed her in front of her terrified and traumatised children, and wrote that it was to teach her a lesson.'

After Ms Griffiths' death, her family paid a moving tribute, calling her the 'very best' mother, sister, daughter and friend.

McFarlane will serve at least 20 years in prison as part of a mandatory life sentence.