A nurse who met her new partner on a dating app not realising he was a convicted child rapist and murderer came home from work to find her two daughters knifed to death.
Police in Russia have launched a manhunt for Vitaly Molchanov, 41, who is missing after the killings of Yana Saprunova, 13, and Elena Saprunova, eight.
Just a month ago the tragic children's mum Valentina Saprunova, 40, uprooted her daughters 1,600 miles from their Siberian home to move into her new boyfriend’s flat, convinced she had found true love.
She took a job at a local hospital in Rybinsk, in the Yaroslavl region, but came home from work to find both girls “literally shredded” by a knife.
Her lover was seen fleeing from the scene on a white bicycle, it is claimed.
The Russian Investigative Committee has opened a criminal case into a double child murder “committed with extreme cruelty”.
The nurse had met Molchanov online via a dating app around six months ago, according to Russian authorities.
In one posting in April, before they moved in together, he wrote: "This is my girlfriend, this is very sad that we are in different cities, but I love her and we can solve all the other issues."
But she was unaware of his shocking past convictions for child rape and murder.
He had been released from prison after serving a long sentence, reports say.
One local newspaper report said: "Vitaly carefully concealed his criminal past from his girlfriend.
"Otherwise, this woman, knowing the crimes for which her lover was sentenced, would in all probability not agree to uproot from the Omsk region to Rybinsk and with her two children to move in with him."
Forensic evidence established both dead girls had been raped before they were killed, said the Russian Investigative Committee in a later statement.
The missing suspect will face two charges relating to sexual violence, police said.
Authorities clarified that Molchanov had been released from jail in December last year after serving a sentence for "especially grave crimes, including murder".
Earlier it was believed he had been released in 2010.
A police statement said: "At present, operational search measures are being carried out aimed at establishing his whereabouts and detaining him."
Russia's senior investigator Alexander Bastrykin today took personal control of the shocking case.
The dead children’s father was revealed to be a retired police major Valentin Suprunov, a former senior criminal investigator. The divorced couple have an older son, Sergey, 19.