State police have identified the tow truck operator struck and killed while helping a motorist in the breakdown lane of the Massachusetts Turnpike. Police say 22-year-old Kevin St Pierre of Southbridge was pronounced dead at the scene after he was struck by an eastbound box truck at about 3 p.m. Wednesday near exit 10 in Auburn. Police said the box truck driver, 45-year-old Richard Taylor of Taunton, was not injured.