The 9-year-old boy was found dead with stabbing wounds in the suspect's basement on Monday evening in the town of Herne, North Rhine-Westphalia. An autopsy on the boy must still be performed, but police believe he was stabbed to death.

Police were first alerted by someone who knew the suspect, Marcel H., who said they had been in touch with him through messaging service WhatsApp. According to the German version of Vice magazine, police confirmed that the chats had included a selfie of Marcel H. with the dead boy.

The chats then ended up on the anonymous online forum 4chan where the poster wrote: “A friend of mine wanted to plan his suicide, but then he killed his neighbour’s kid because he messed up the suicide attempt”.

According to DPA, it is not clear who published the chats on the forum. Police have also stated that Marcel H. seemed to be contemplating suicide.

Police had said on Tuesday that a video of the suspect had also been posted on the restricted access darknet network, but officials later clarified that what had been posted was pictures.

Investigators are now looking into possible evidence of another crime by Marcel H. On Tuesday someone on an online chat forum identified themselves as the suspect, posting pictures and stating “I cut my hand as I fought a 120 kg beast”.

“She put up more resistance than the kid,” the person wrote, according to police. “I tortured out of her the data for her bank, PC and phone, therefore I cannot publish the name.”

Police are now asking that anyone who knows of a missing woman come forward, but have also said that they cannot rule out that the new online posts were fake.

Officials have warned that anyone who recognizes Marcel H. should not approach him, but rather call police as he may be dangerous.

He is described as 1.75-metres tall, blond and thin, possibly wearing glasses with camouflage pants and vest.

Marcel H. is unemployed and believed to have been living alone in the house. The family was reportedly supposed to move and his parents were no longer there.

He also reportedly had little social contact with others, and was not previously known to police.

Photo released by Bochum police of the suspect.