A mating date for two polar bears went badly wrong at a Russian zoo when the male suddenly killed the female as she rejected him as they were poised to copulate.
Aurora had been moved 1,900 miles from Krasnoyarsk in Siberia to Izhevsk in the Urals to be introduced to giant male Baloo.
Perhaps there was a clue of trouble ahead in their first meeting when a video shows how she inspected the male, before turning and walking in the opposite direction.
Yet during a two-week 'courtship' they played, basked in the sun, and swam together, and it appeared Aurora was 'receptive'.
Keepers watched and waited for the key moment - but it ended in tragedy.
Head of Royev Ruchey zoo in Krasnoyarsk, Andrey Gorban, said: 'At the very moment he mounted her, something went wrong.
'Aurora showed her character, and Baloo was furious.'
The aggressive attack is believed to be the first of its kind in captivity.
Zoo staff threw water and shot a sedative at Baloo but it was too late.
In seconds he had savaged and killed the smaller female.
'He fell near Aurora but she was already dead,' he said.
'Everything happens in nature, but in zoos this is the first case, and we will carefully study what happened, both for ourselves and for science,' said Gorban.
'I haven't studied it thoroughly so far, but world-class specialists cannot remember such cases in zoos.
'It was a completely unexpected outbreak of aggression.'
A male could kill a female for food but 'not during estrus' - the period of sexual receptivity and fertility in female polar bears.
He told zoo visitors on social media: 'It is unbearably hard to report this tragic news.
'Our Aurora is gone.
'Just the day before yesterday we were happy that our white giants found each other, loved each other.
'We were hoping to see the offspring.
'Spacious enclosures for little cubs were already being built in (our zoo).
'But the sudden conflict crushed our hopes…. only emptiness is left.'
A statement from Izhevsk Zoo said: 'The reason for the conflict between two recently completely peacefully coexisting polar bears Aurora and Baloo remains a mystery.'
This article has been adapted from its original source.
© Associated Newspapers Ltd.