Police Scotland say the "targeted attack'' happened at the man's home in Uddingston.
Killing Of Foster Carer 'Might Have Been Avoided'
The death of a woman killed by her 13-year-old foster child might have been avoided, an inquiry has concluded.
Dawn McKenzie, 34, was stabbed by the teenager she and her husband Bryan were looking after at their home in Hamilton, South Lanarkshire, in June 2011.
The boy, who is referred to only as child D for legal reasons, was detained for seven years in 2012 after admitting culpable homicide on the grounds of diminished responsibility.
A fatal accident inquiry into the circumstances of her death was held earlier this year before Sheriff David Bicket in Motherwell, North Lanarkshire.
He concluded that her death might have been avoided had Foster Care Associates Scotland (FCAS), an independent fostering agency which arranged placements at the request of Glasgow City Council (GCC), ''taken proper account'' of the couple's lack of experience as foster carers.
The inquiry was told that Mrs McKenzie had applied to FCAS after seeing a newspaper advertisement.
She and her husband had expressed a preference to foster children aged between one and eight but the older boy, who had a troubled background, was placed with them in November 2010.
The sheriff found there were ''no defects in a system of working'' which contributed to the death of Mrs McKenzie.
He said: ''From all the evidence that I heard no-one could have predicted that child D would have acted in the way in which he did, and no-one could have predicted the tragic consequences for a dedicated and caring foster carer such as Dawn McKenzie.
''It is clear that both GCC and FCAS take their responsibilities extremely seriously and they have taken on board changes needed to practice and to promote the safety of foster carers and children in care.''
But he emphasised that the McKenzies were new foster carers embarking on their first placement who had no children of their own and only limited experience in caring for Mrs McKenzie's nephew.
He said: ''The death of Mrs McKenzie might have been avoided if Foster Care Associates Scotland, when considering if they had a suitable placement for child D when so requested to do so by Glasgow City Council, had taken proper account of Mr and Mrs McKenzie's status as new carers, and lack of suitable prior experience of adolescent aged children such as child D and accordingly had not recommended them as suitable prospective carers for child D.''
The inquiry was told that in the days before she died, Mrs McKenzie had confiscated the boy's laptop and mobile phone after discovering he was having unsupervised Facebook contact with his mother.
On the day of the attack the boy had been grounded after failing to return home from school on time.
Mr McKenzie had left the house to spend the evening with his brother-in-law when his wife was stabbed 10 times, including a fatal wound to the abdomen.
A significant case review commissioned by Glasgow child protection committee found in 2013 that Mrs McKenzie's death could not have been foreseen or prevented.
However, the nine-member review team also concluded that shortages in staffing and resources affected the care of the boy in question.
Estella Abraham, chief executive of Foster Care Associates Scotland, said: ``Dawn McKenzie was highly regarded as a child care worker before becoming a foster carer with FCA Scotland.
''Sheriff Bicket has recognised that in a short space of time she made a positive contribution to a young person's life. Today our thoughts are with Dawn's family and Bryan in particular and we wish to express our sincere condolences to them.
''The conclusion of the inquiry was that Dawn's death was the result of an entirely unpredictable event.
''We will now reflect on the full findings and the recommendations made in the judgment to ensure that the foster care provided in Scotland continues to be the best it can be for the children involved and the families who care for them.''
A spokesman for Glasgow City Council said: ''This has been an incredibly distressing case and our thoughts remain with Mrs McKenzie's family.
''While Sheriff Bicket is clear that nothing could have predicted this tragedy, we believe it is appropriate to take time to give his findings the consideration they deserve before commenting in any detail.
;;A report that will consider the implications of the sheriff's findings for the council and what action we require to take as a result will be submitted to our children and families committee as soon as is reasonably possible.''
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