(WATERTOWN TOWNSHIP) -- Sanilac County Sheriff's deputies were sent to 600 S. Sandusky Road Tuesday morning after a report of an individual run over by a semi-truck at Peter Northrup Enterprises. Deputies learned that the owner of the business, Peter Northrup, Jr. and his 34-year old son Peter Northrup III, both of Sandusky, had been working on one of the company's semi trucks. Peter Northrup Jr. crawled under the semi to retrieve a tool, when his son backed over him. The 56-year old Sandusky man was transported to McKenzie Health System and later air lifted to Hurley Hospital in Flint for treatment of serious, non-life threatening injuries. Deputies were assisted by the Sandusky Police Department, Sandusky Fire and Sanilac EMS.