Aid worker Linda Norgrove was killed by a grenade thrown by a US special forces soldier sent to rescue her, a joint US-UK investigation has found.
Ms Norgrove, 36, from Lewis, Scotland, was taken hostage in Afghanistan in September. She died on 8 October.
It had been thought she was killed by her captors.
Foreign Secretary William Hague said US soldiers had been disciplined for not informing commanders immediately that the grenade was a suspected cause.
He revealed the results of the probe in a statement to the House of Commons.
An investigation team of 10 staff spent almost three weeks in Afghanistan interviewing all involved in the rescue attempt.
They also had access to video footage, reports and post-mortem examination results which showed Ms Norgrove died of “penetrative fragmentation injuries” to her head and chest.
“When the grenade was thrown no member of the team had seen, or heard, Linda Norgrove”
William Hague Foreign Secretary
Mr Hague said: “After the investigation is clear that these injuries were caused by the grenade.”
He said US special forces had not immediately notified officers further up the chain of command about the grenade.
Mr Hague said this was in breach of military law and a number of soldiers had been disciplined.
Before making his statement, Mr Hague met with the Scottish aid worker’s parents John and Lorna Norgrove.
In a statement, the family said: “We are grateful to have been briefed in detail by the UK and US military officers who led the inquiry into Linda’s kidnapping and subsequent failed rescue attempt.
“We would like some time to digest this and the contents of the report before we make any further comment.
“We will issue a statement early next week and would ask the media to respect our privacy in the meantime.”
The foreign secretary said that with the agreement of the prime minister he had agreed to a rescue bid because of fears that Ms Norgrove’s life was in “grave danger”.
He said an incredibly difficult operation was launched by highly experienced personnel in extreme mountain terrain at night.
After being dropped off by two helicopters, one of two teams moved along a narrow ledge and came under attack.
Mr Hague said it was believed Ms Norgrove was being held in buildings higher up a mountain.
He said: “A grenade was thrown by a member of the rescue team who feared for his own life and those of his team towards a gully from where some of the insurgents had emerged.
“When the grenade was thrown no member of the team had seen, or heard, Linda Norgrove.”
Following the operation Ms Norgrove’s body was found in the gully.
She had been working for American-based aid organisation Development Alternatives Inc (DAI).
On 26 September, she was kidnapped in the Dewagal valley in the Kunar province while looking into the development of agricultural projects in the east of Afghanistan.
Her funeral was held on Lewis in the Western Isles.
An inquest into Ms Norgrove’s death was opened and adjourned by Wiltshire coroner David Ridley in Salisbury in October.
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