Investigators hunting a sniper responsible for 10 attacks in the Washington area prepared to release their first wanted poster – a drawing of a white box truck – after it was confirmed today that an eighth death had been linked to the killer.

Millions of terrified residents around Washington stayed locked in their homes today after an eighth killing was linked to the serial sniper stalking the area.

A businessman shot while a police officer stood just 50 metres away was the 10th victim of a sniper who has been stalking the Washington area, police confirmed today.