Unfortunately in this case, the loaded gun (ready to fire, no safety latch apparently on) was accessible to the child, and even though his father was just next to him, a small gap in time ensured that the child was able to pick up the gun and fire at himself, leading to his tragic death (link to article):
Manal Jr. was sitting on a stool beside his father at the store on Sunday when he found a handgun stored on a shelf beneath the cash register. The three-year-old accidentally shot himself and died shortly after. It is illegal in North Carolina to have an unsecured gun in the presence of a child, according to the Associated Press. Authorities in Lumberton, a small city 100 miles south of Raleigh, are investigating the incident and the Robeson County District Attorney's Office will decide whether to file charges. Lumberton Police Department Capt. Terry Parker urged gun owners to keep their weapons secure. "Make sure it's where the child cannot have access to it," he told WTVD Monday. "Kids are going to be naturally curious about firearms. Kids, they need to learn gun safety but at the same time we as adults have got to protect the kids to the best of our ability."