The crash happened shortly before 9 am on Saturday, when a Mercedes CLS 350 (said to be worth around €70,000) carrying five people was speeding along a country road near the village of Hardebek, Schleswig-Holstein.
Apart from the 26-year-old driver, the car was carrying four passengers: a 23-year-old woman and three of the driver's friends, aged 23, 24, and 46, the Bild newspaper said on Tuesday.
The luxury car reportedly hit the kerb and was sent flying almost 100 metres before smashing into a tree. The three male passengers were killed immediately, but emergency workers were able to pull the young woman from the wreckage alive.
The 26-year-old driver was left trapped under the engine of the car for 90 minutes, after which emergency doctors decided the only away to save his life was to amputate both his legs.
He was then rushed to a hospital in Hamburg, where he and the young woman were said to be in critical condition.
Police reported on Monday that the 46-year-old man killed was vice-president of the Rügen chapter of the Bandidos. The group was apparently on its way to the opening ceremony of a new clubhouse in the town of Wahlstedt, Schleswig-Holstein.
Despite the Bandidos' links with organized crime, police do not suspect foul play. Investigators believe the driver was drunk.