Police are investigating a six car pile-up in Eastbourne.
It happened on Grand Parade last Wednesday (25 May) at around 12.45pm close to the junction with Howard Square.
Several people were treated at the roadside for minor injuries by both South East Coast Ambulance personnel and members of the London Ambulance Service, who were in town on a training exercise.
Two people were taken to hospital for treatment but were later released..
PC Dan Cloake, of Eastbourne Police, said: "A man was seen running from the scene but was detained by an off-duty police officer. We'd like to hear from anyone who saw the crash or the man running away."
Anyone with information is asked to email firstname.lastname@example.org or phone 101, quoting serial 597 of 25/05.
Alternatively they can contact the independent charity Crimestoppers anonymously on 0800 555 111 (www.crimestoppers-uk.org).
A 27-year-old man has been arrested on suspicion of aggravated taking a vehicle without consent and not being insured to drive. He has been bailed to Friday, 29 July while enquiries continue.