A 79-year-old Shrewsbury man was killed in an accident involving a backhoe in Westborough on Friday, authorities said. Robert Shaughnessy was treated at the scene on Otis Street and taken to UMass Memorial Medical Center, where he died from his injuries, Westborough police said in a statement. Details of the accident were not immediately clear. The backhoe, which is owned by Grant Services Inc., was driven by Robert W. Goulding, 36, of Whitinsville, police said. He suffered non-life-threatening injuries and was also taken to UMass, according to police.