A dad diagnosed with a terminal brain tumour killed his teenage son because he felt his wife would not be able to raise the boy after he died, it is reported.
Oleg Drachev, 40, also tried to stab his wife - whose name was not given - but she managed to lock him in the bathroom and call police for help.
He has been detained on suspicion of murdering his 13-year-old son, Ilya, as the boy slept at the family home in Moscow.
They were known as a happy and devoted family until the dad's recent diagnosis of an incurable brain tumour, according to reports.
Drachev, a design engineer who formerly served in the army, spent all his spare time with his son, say devastated family members.
They went hiking and swimming, and together constructed outbuildings at their summer house and a kennel for their dog.
Drachev told detectives he feared that no-one could take his place in raising his son after he died, Moskovsky Komsomolets reported.
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.
Drachev's 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.