A father with a terminal brain tumour stabbed his 13-year-old son to death because he feared his wife would not be able to raise the boy by herself, say reports.
Oleg Drachev, 40, has been detained on suspicion of murder in Moscow, police said.
He also tried to stab his wife – whose name was not given – but she managed to lock him in the bathroom and call police.
The couple and son, Ilya, were known as a happy and devoted family until his recent diagnosis with an incurable brain tumour, say reports.
Drachev, a design engineer who formerly served in the army, spent all his spare time with his son, according to his family.
They went hiking and swimming, and together constructed outbuildings at their summer house, and a kennel for their dog.
He feared that no-one could take his place in raising his son when he died, he told interrogators, reported Moskovsky Komsomolets.
He did not see how his wife could pay their mortgage and bring up the child, he said.
He stabbed his sleeping son after she had gone to work.
When they didn’t answer phone calls, she rushed home, broke in through a window, and found her son dead in bed.
Drachev then attacked her with a knife, but she fought back and locked him in the bathroom.
His mother told Moskovsky Komsomolets newspaper: ‘You cannot even imagine how he loved his son.
‘He never punished him. Mostly his mother told him off.
‘But after the cancer diagnosis, he went crazy.’
The detained father is undergoing an examination at a secure psychiatric hospital in Moscow.