Less than $20 (£15) was stolen, the Charlotte Observer newspaper reported.
Neighbours told WCNC-TV that the boy's organic lemonade stand is well known in the neighbourhood, and that he is an entrepreneur who also mows lawns in the community.
"It's heart-wrenching. That little boy will never be the same", Smith said.
"Never thought in a million years I'd be racing off to pick him up with somebody pointing a gun at him and taking his money from just a simple thing of selling lemonade", said Philip Smith, the boy's father.
Deputies found the camo hat and a BB handgun stashed in a wood near the residential tract and are asking the public's help in tracking down the suspect.
He said that nowadays, "Criminals are very bold" and that "this is a new low".
According to WSOC, an ABC affiliate of WHSV, the boy was saving money in order to buy a lawnmower.
The young boy was back selling lemonade Sunday.
The police have been unable to locate the suspect so far.