Luis Morales said sales at his McAllen gun shop are up 50 to 60 percent from less than a year ago.
"There's been an increase in home invasions and crime," said Morales. "What people are doing is you know buying guns to defend themselves or property in their homes."
But the weapons sold at Resilient Defense Systems in McAllen aren't typical.
Instead, the gun shop specializes in fully automatic and suppressed weapons.
Many are similar to what the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) continues confiscating in the United States and across the border.
"It's an issue of supply and demand," said Armando Salas, assistant special agent with the Houston division of the bureau. "The closer you are to the border, the more firearms you're going to end up selling."
Salas said although many of the guns they seize are traced back to the United States. He doubts licensed gun dealers are to blame.
"It's very difficult for licensed dealers to be able to tell whether or not those sales are for legitimate purposes," said Salas.
Salas said licensed gun shops like Resilient Defense Systems are required to record firearm sales.
Once the weapon is sold, though, that purchaser can sell it to someone else without facing the same rules.
"Other people who have firearms are not required by law, they can dispose of their weapons without requiring any kind of identification, without running any background checks," said Salas.
ATF agents believe that's how the weapons can end up in the wrong hands.
"Sometimes they're stolen, sometimes they're sold, sometimes they're engaged illegally in the activities," said Salas.
The ATF said most weapons they seize are traced back to the U.S.
They said that's partly because the United States may be the only country that puts serial numbers on weapons and keeps records of their sales.