Police are hunting a woman on a mobility scooter who struck a grandmother and young child.
The accident happened at William Street in Londonderry at about 11.30am on Thursday.
It is understood the woman and her grandson, who was in a pushchair, were knocked down as they stood on a footpath.
The Police Service of Northern Ireland have confirmed they are investigating and have appealed for information.
Officers are keen to hear from a woman who helped at the scene.
Anyone with information is asked to contact police on the 101 non-emergency number.