The cyclist, a man around 30 years old, was brought to hospital after the shooting, which took place at 4.20 pm, but died of his wounds shortly afterwards.
He had sustained a bullet wound in the head as well as several in his chest, the Hamburger Abendblatt reports.
The victim's identity had still not been clarified on Monday morning.
Police also say they have no leads as to the identity of the gunman.
Witnesses have described him as being between 20 and 25 years old and wearing shorts, a white T-Shirt and a dark baseball cap.
A 34-year-old driver was also directly next to the scene of the shooting as it took place.
After she had stopped at a bridge to let an oncoming car through, she looked out her left-hand window and saw a man holding a pistol.
“I saw him aiming in our direction,” she said.
She immediately accelerated but by that time he had already fired his weapon..
After driving 300 meters she noticed that her rear tyre on the lefthand side was flat. It had been punctured by a gunshot.
The woman and her 6-year-old son did not sustain injuries in the incident.
“We are a bit shocked,” she said.