Anatoliy Trapko, 28, attempted to rape the girl, and killed her after he failed because of 'sexual problems', say police.
Police say Trapko - waiting in his taxi - confessed to starting a conversation with the girl and asking if she wanted to see a kitten. She refused but he persuaded her to get in his car. Trapko, pictured from his back on police footage released by NTV channel shows where he left Anastasiya's body
At the time his wife Svetlana was close to giving birth to a baby daughter.
Nastya Lutsishina, from Ussuriysk, vanished on 19 February after her physical education class finished ten minutes early. Hundreds of volunteers hunted for the schoolgirl before her body was found in woodland near the city in the Russian Far East.
Her track and field training session ended ten minutes early before her mother came to collect her, and Nastya stayed to walk the 100 metres home.
Nastya's death caused enormous shock in Ussuriysk with reports that large numbers of locals would attend her funeral. Pictures: Ussuriysk police footage
Police say Trapko - waiting in his taxi - confessed to starting a conversation with the girl and asking if she wanted to see a kitten. She refused but he persuaded her to get in his car. He said they would need to drive some distance.
But he took her 15km outside the city and tried to rape her. He failed due to 'sexual problems'.
He became angry and took a knife, stabbing her twice, once in the neck. Then he found a remote place 150 metres from the road and hid her body.
As the search was underway, on 23 February his wife Svetlana, 30, gave birth in a city hospital.
The same day the girl's body was found. A day later he celebrated his 28th birthday.
Trapko pictured on his wedding day to wife Svetlana. Picture: LifeNews
Trapko did not visit his baby daughter or wife before his arrest, it is understood.
Police said that dashboard cameras were crucial to entrapping the suspect. Footage from these cameras - now popular with Russian drivers - was a 'major aid' in tracing him. An eyewitness had seen the taxi driver talking to the girl, and a driver had footage showing her getting into his car.
'The taxi driver detained on Saturday gave the confessing testimony and told about details of the crime,' said spokesman for the Russian Investigation Committee Vladimir Markin.
'The knife was found at his house that was reportedly used for inflicting two knife wounds to the girl.'
Earlier a local police source told Ussur news website: 'The child was killed. There were multiple wounds on her body. There are reasons to think that the criminal raped the girl'.
Her body was found on 23 February some 15 kilometres from Ussuriisk and 150 metres from a road leading to the village Banevurovo in Ussuriisk district.
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