No person, firm or corporation that engages in the retail sale of goods, where the principal part of such trade or business is the retail sale of goods other than firearms, shall employ a person to sell firearms in a retail store unless such person (1) is at least eighteen years of age, (2) has submitted to state and national criminal history records checks and such checks indicate that such person has not been convicted of a felony or a violation specified in subdivision (2) of subsection (b) of § 29-36f, and (3) has successfully completed a course or testing approved by the Commissioner of Emergency Services and Public Protection in firearms safety and statutory procedures relating to the sale of firearms. The sale of firearms by such person, firm or corporation shall be accomplished only by an employee qualified pursuant to this section. Any employer who employs a person to sell firearms in violation of the provisions of this section shall be liable for a civil penalty of not more than ten thousand dollars per day for each violation. The Attorney General shall institute a civil action to recover such penalty.