The break-in was discovered Saturday morning when the shop's owner arrived to open the store for the day.
The boys, ages 16 and 17, are believed to have taken nine handguns. They got into the store through a smashed window, police said. Wires to a security camera just above the window were also cut. Other security cameras inside the store show one of the teens grabbing guns from a display case and ammunition from a shelf.
The boys were arrested early Sunday when a police officer spotted one of them standing outside the building while the other two were inside. Police suspected the group returned to steal more guns.
The boys are expected to be charged as adults today. Their names will be released following their arraignment.