Police in the German state of North Rhine-Westphalia launched a manhunt on Tuesday. The news followed the announcement that a 19 year-old man is suspected of having killed a 9 year-old boy before bragging about the murder in a video posted online.

Authorities were tipped off on Monday after people who had viewed the clip on the darknet alerted the police. The darknet, also known as the dark web, is another name for World Wide Web content that requires special encryption software or authorization to access, and is used by privacy advocates as well as criminals.

After being alerted, police found the victim's body in the basement of the suspect's home in the town of Herne on Monday evening. Teenager Marcel H. was described as unemployed and unsociable, but did not have a criminal record.

"The victim and the suspect lived next door to each other," a police spokesman told the press, adding that they would not yet speculate on the man's motive. Police warned the public that Marcel H., who they described as "dangerous," was approximately 1.75 meters (five foot seven inches) tall, blond and of slim build. He was thought to be wearing military-style fatigues and could be armed.

Herne town Mayor Frank Dudda said that his community was "bewildered and shocked, and we are mourning with the family."

Officers were using helicopters and sniffer-dogs as well as large-scale search party to try and track down the suspect.

es/se (AFP, dpa)