It happened on the A259 South Coast Road at Peacehaven at around 11.10pm on Saturday (April 30) when an unmarked police car was involved in a collision with a 27-year-old man who was on foot. The man was sadly confirmed dead at the scene a short time later.
After being notified by Sussex Police we sent investigators to the scene and the police post incident procedure and later declared an independent investigation.
Sussex Police said they are fully co-operating with the independent investigation.
IOPC regional director Graham Beesley said: "Our sympathies are with the man’s family and everyone else affected by his death. We will be in contact with the man’s family to explain our role and will keep them regularly updated on our progress.
"We appreciate there has been concern expressed in the community about exactly what happened on Saturday evening and we are working hard to establish all of the facts.
"We are looking at the circumstances leading up to the collision and the actions of the police in the immediate aftermath.
"We have already received dashcam footage from a member of the public who was driving in the area at the time and we are analysing that along with footage from the police car involved in the collision.
"Initial accounts from the police officers involved have been provided and we are also gathering police body worn video and radio transmissions.
"We know that a number of people were at the scene following the collision and we would appeal to anyone with information to come forward and talk to us. We would also like to hear from anyone with mobile phone or other footage they may have recorded of the incident."
Sussex Police Chief Superintendent Jo Banks said: "Our thoughts are with the family and friends of the man who tragically died in this collision.
"We recognise the impact of this incident on his family and the local community and we are fully co-operating with the IOPC to ensure a full and fair investigation.
"The IOPC are liaising with the family and as such we are unable to provide further information."
Anyone with information is urged to call 0300 3035612 or email [email protected] as soon as possible.
IOPC investigators will be in the area in the coming days to locate any other CCTV footage that might be available, and to carry out house to house inquiries to identify witnesses.
The Coroner has been informed and a post mortem examination is expected to take place later this week.