Dozens of people protested outside Sussex Police headquarters on Saturday - one week after the death of Arthur Holscher-Ermert.
The 27-year-old was struck by an unmarked police car at 11:10 last Saturday night in Peacehaven. He was pronounced dead at the scene.
Demonstrators at the protest included Arthur's brother, his father and his girlfriend who are calling for justice.
Arthur's brother, Karl Holscher-Ermert, told ITV Meridian: "It's been seven days since this incident, but we have no answers."
"I have not grieved. I've not at a chance to grieve. I've had no help from anyone."
Karl added: "The truth needs to come out. The truth needs to prevail and justice needs to be provided."
The Independent Office for Police Conduct is reviewing dashcam footage and video from body worn cameras to establish exactly what happened.
The driver of the unmarked police vehicle is under criminal investigation for causing death by dangerous driving.
Superintendent James Collins from Sussex Police said: "We understand the strength of feeling following the tragic death of Arthur Holscher-Ermert and will facilitate a peaceful protest.
"We are providing every assistance to the IOPC to allow for a thorough investigation and for the family to receive the answers they need.
"Our thoughts are with Arthur's family and friends and we would ask the public to allow for the investigation to take its course."
The IOPC is calling for witnesses or anyone with footage to come forward while their investigation continues.