Gerwald Claus-Brunner
Gerwald Claus-Brunner killed himself on the weekend his Pirate party was voted out of Berlin's parliamentGetty

A prominent figure in Germany's Pirate Party is believed to have murdered a party activist and wheeled his body through the streets of Berlin before going on to take on his own life.

Prosecutors said Gerwald Claus-Brunner, a 44-year-old former MP who lost his seat in the Berlin state parliament at the weekend elections, had confessed to the murder-suicide in a letter sent to a colleague.

He was found dead in his apartment in the suburb of Stieglitz on Monday (19 September) together with the body of a 29-year-old man.

Local media reported the victim, identified as Jan Mirko L, had previously worked for Claus-Brunner's parliamentary office and had filed a stalking complaint against the politician in June.

Claus-Brunner, known for his eccentric dress-sense of bandana and dungarees, was said in an autopsy report to have taken his own life, while the other man died after suffering "blunt force to the upper body".

Prosecutors claim the politician killed the man on 15 September at the victim's apartment, before moving the body to his own flat.

According to German tabloid Bild, Claus-Brunner may have used a sack barrow to transport the body 11km across Berlin to his own apartment after CCTV images showed him wheeling a large black box. This has not yet been confirmed by investigators.

Claus-Brunner, who was openly bisexual, had repeatedly referred to the victim on Twitter with the affectionate name "curly head" in the months leading up to their death, according to Die Welt. The day after he is believed to have killed the man, on Friday, he tweeted: "My love, my life, for ever and ever, for you, my dear curly-head."

Another sent the same day reportedly read: "A really shit day today, worse than all the bad days I've had before. Hopefully the weekend will be better."

The prosecutor explained the motive for the alleged murder only as for "highly personal reasons" and said the contents of the confession letter meant the case was considered closed.

The Pirate Party wrote on its website that Claus-Brunner had been suffering an "incurable illness".

"Faxe, as we all called him, was always controversial, never simple and did not have it easy. Every one of us has a story to tell about him," the statement read.

The party entered Berlin's state parliament in 2011 on the back of a digital rights agenda. Sunday's elections saw its 8.9% share of the vote plummet to 1.7%, with Claus-Brunner gaining 2% of the vote in the Steglitz-Zehlendorf district.

German media, citing sources in the police investigation, said Claus-Brunner is believed to have died before the day of the election, on either Friday or Saturday.

He spoke in the Berlin parliament for the last time in late June, saying he predicted his party would lose its seats after the election.

"In this current legislature, you will also stand up and have a minute's silence for me at the beginning of the plenary meeting," he had said.