Deputies responded to a report of multiple gunshots heard coming from the We Buy Gold shop located at 3301 Middlefield Road in unincorporated San Mateo County near Redwood City at about 6:40 p.m. Thursday, officials said.
When deputies arrived, they found the business to be locked, but saw four men and a small child inside, according to sheriff's officials.
Several firearms, expanded casings and stolen computer equipment were found inside the business.
An investigation determined that an AR-15 type assault rifle and a shotgun were negligently discharged inside the building.
A 3-year-old boy was inside at the time of the shots being fired, but no one was injured by the gunfire, sheriff's officials said. The boy was released to his mother.
The two owners of the business - 23-year-old Pedro Aguilar-Baltazar and 34-year-old Jorge Conde-Cardona, both of Redwood City - were arrested.
Baltazar and Cardona were booked into jail on suspicion of child endangerment, negligent firearm discharge and possession of stolen property.
Two other men inside the business were found to have been uninvolved in any criminal activity and released, according to sheriff's officials.
Anyone with information about the incident is asked to call (650) 363-4363 or (650) 363-4057, or anonymously at (800) 547-2700.