The victim's sister, Emma Gowing, told the court in a victim impact statement
My sister was a vibrant, wonderful woman, who lived life fully, with love, compassion, fun, adventure and joy. Our lives will never be the same.
That man has caused my family unimaginable pain, suffering and grief and the recurring nightmare of what he did to her before she died.
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No one has immediately claimed responsibility for the attack.
Met Office says it is set to be “a glorious day” in most areas
He had been in the US to attend the Def Con hacking convention.