A 19-year-old man is being hunted on suspicion of murdering a nine-year-old boy in the west German town of Herne and boasting about the killing in an online video.
Police in the city of Bochum said authorities received a call late on Monday from a member of the public who feared a killing had taken place in the nearby town of Herne.
Officers then searched the basement of a house in the town and found the body of the boy, said police spokesman Volker Schuette.
The victim and the suspect were neighbours, he said.
The suspect - named by police as Marcel Hesse - allegedly bragged about the killing in a video on the so-called "dark web", an area of cyberspace which is invisible on the open internet and used by some for illegal activity.
‘Armed and dangerous’
Police warned that Hesse, who is unemployed and was previously unknown to police, could be armed and dangerous.
He was described as thin, of average height, with short blond hair and glasses, and wearing clothes with a camouflage pattern.
North Rhine-Westphalia's top security official, interior minister Ralf Jaeger, said the images posted online "left even the investigators stunned".
Hesse was clearly identifiable, standing with blood-stained hands next to his alleged victim, police said.
Police are using helicopters and sniffer dogs to search for Hesse.
PA