The suspect, 26-year-old Jan O., referred directly to the murder on his own Facebook page, the Göttinger Tageblatt reported. The police immediately shut down the page because it constituted evidence.

“Butchered a girl yesterday. One every day until they catch me,” he wrote, according to the paper.

He is thought to have posted the remarks last Wednesday after he killed 14-year-old Nina.

On other social networking sites, which have also since been closed down, Jan O. sought contact with young girls. The crime has cast a spotlight on such social networking sites, on which Jan O. reportedly appealed to girls “aged 10 to 16.”

Police have described the learning-disabled, alcohol and drug-abusing unemployed man as a potential serial killer.

They are now investigating whether Jan O. is responsible for other crimes in the region of Northeim, Lower Saxony. State prosecutors were also assessing whether the man, from the town of Uslar, was mentally ill.

Click here for a gallery of the investigation in Bodenfelde.

He is alleged to have brutally killed Nina, 14 and Tobias, 13. Police believe he stabbed and choked Nina early last week and Tobias on Saturday. Their bodies were found on Sunday near one another in a wooded area on the outskirts of Bodenfelde, where they lived.

Police arrested Jan O. aboard a train at Bodenfelde on Monday night. They were led to him in party through a girl whom he approached on Saturday afternoon, giving her his mobile phone number.

Prosecutors have said for two days they expected an imminent confession from Jan O., though so far none has been announced. They now say they expect to make a further announcement on Friday.

The Local/dw