A U.S. Army veteran who served in the war in Afghanistan pleaded not guilty Wednesday to fatally shooting a homeless man with an automatic rifle in downtown Memphis. A lawyer for Karl P. Loucks, 42, entered the plea to a first-degree murder charge during a hearing in Shelby County Criminal Court. Loucks also pleaded not guilty to an aggravated assault charge in the stabbing of another homeless man in downtown Memphis, where Loucks lived in an apartment. Loucks is being held in jail without bond. He was arrested May 31 in the killing of Shaun Rhea. Loucks’ lawyer has…..