A terminally ill dad killed his 13-year-old son fearing his wife wouldn't be able to raise him alone, say reports.
Oleg Drachev, 40, has been detained on suspicion of murder in Moscow, Russia, according to local police.
The man, who has an incurable brain tumour, is alleged to have tried to stab his wife - whose name was not given - but she managed to lock him in the bathroom and call cops.
The young family was known to be happy and devoted until Drachev's recent diagnosis, it has been claimed.
Drachev, a design engineer who formerly served in the army, spent all his spare time with his son, Ilya according to his family.
Father and son went hiking and swimming, and together built outbuildings at their summer house, and a kennel for their dog.
He told police he didn't want anyone else to take his place in bringing his son up and worried how his wife would pay their mortgage when he died, reported Moskovsky Komsomolets.
The "devoted" dad stabbed his sleeping son when his wife had gone to work.
Not being able to reach her husband or son by phone, 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.