By Jay Paul and Nathan Layne CHESAPEAKE, Va. (Reuters) -A manager at a Walmart Inc. store in Virginia entered a break room and opened fire on fellow employees before turning the gun on himself, an eyewitness said on Wednesday, leaving a total of seven dead in the latest mass shooting in the United States. The gunman, identified as Andre Bing, 31, of Chesapeake, Virginia, said nothing as he began firing on the workers gathered ahead of their shift late Tuesday, Walmart employee Briana Tyler told ABC’s “Good Morning America.” “I looked up and my manager just opened the door and he just opened fi…