Police are asking the occupants of a blue car who stopped to offer help after a collision on the A75 to come forward.
Kieran Currie, 19, was hit by a lorry outside Newton Stewart on Saturday morning and has died from his injuries.
He was struck at around 2.40am on Saturday morning and died later in hospital. It is believed he had been walking home from a party at the time.
Now police want those in the blue car to step forward and contact them to help them piece together the events of the incident.
Police closed the road to carry out a full investigation and diversions via Ayr and New Galloway were put in place. The road reopened at around 9.30am on Saturday.