The body of 43-year-old Uwe Sattler was found in the River Elbe in July by a fisherman. He was wearing a rucksack full of rocks and had been shot in the head and put into a sack fastened with cable ties before he hit the water.
Local media was rife with speculation about a Mafia murder - but after extensive investigation, the police now say they are nearly certain that the Sattler killed himself.
"We are 99.999 percent certain it was suicide," a Hamburg police spokeswoman told The Local.
"There is no other explanation; no other motive and no other evidence."
Detectives have worked out that there was enough of an opening in the sack between the cable ties for Sattler to get an arm out and shoot himself so that afterwards the gun would fall to the ground. He would have had to have done this while perched on the edge of a bridge or jetty to ensure falling into the water.
Why he would make such an effort to do this remains a mystery - as does the whereabouts of the gun, which was never found. "It just goes to show, there is nothing that does not exist," the police spokeswoman said.
After using fingerprints to identify the body, police went to his flat in Hamburg which reportedly looked newly renovated - and held absolutely no furniture. Officers found only a small box of documents, including a note to say that the belongings in the cellar should be given to the building landlord, Die Welt said.
Back in the summer when detectives were trying to piece together Sattler's life, they also found little to work with. He was single and unemployed, and seemed to have no friends, nor any contact with his family. Despite intensive efforts, the police admitted in July that they had been unable to find a single friend or acquaintance.
He had moved from Berlin to Hamburg in September 2008, but no friends could be found in the capital either. Die Welt said that he had rented a van in 2004 and crashed head-long into a bridge pillar. He survived the crash but was seriously injured. When police went to his flat after the crash they found it was completely empty just like his place in Hamburg.
This would seem to be reason to suggest he was suicidal - although might leave open some questions about the immensely complicated method he supposedly chose in Hamburg.
The investigation has been put on ice, but the case remains open.