Store employee uses shotgun to frighten off attacker, MLive.com, Michigan, 07/18/14

An employee of Brother’s Market in Flint, Mich. ordered a man to leave the store after he spotted the man attempting to shoplift. Before the alleged shoplifter left, he threatened to come back to the store and shoot the employee. Roughly two hours later, the man returned to the store and pointed a gun at employees. However, one of the employees responded by retrieving a shotgun, which prompted the criminal to flee.
Police caught up with the criminal a short time later. Having been previously convicted of a felony, the man faces federal gun charges. 

Mother of two defends family from criminal wielding a machete and shotgun, WOOD, Grand Rapids, Mich. January 31, 2014

A mother of two was upstairs at home with her children in Iona County, Mich. when she heard a suspicious noise coming from the first floor. The woman retrieved a gun, went to the top of the stairs, and spotted a masked criminal armed with a machete and a shotgun through a window next to the home’s front door. The armed homeowner raised the firearm at the criminal, prompting the would-be intruder to retreat from the door.
Eventually police arrived on the scene and captured the suspect, following a brief chase. In an interview with a local media outlet following the incident, the armed mother stated, “I honestly think the gun saved my life.” 

Store owner stops shotgun toting robber, WPMI, Mobile, Ala. 04/29/13

A robber toting a shotgun entered Sandie’s Beer Wine and Spirits in Irvington, Ala., put the gun to the owner’s head and demanded the money in the register. The owner responded by retrieving a gun and firing at the criminal, striking him in the torso and causing him to flee in a getaway car. Police captured the robber a short time later.
Recalling the incident to local media, the owner stated, “He had a shotgun and held it to my head. I saw my life passing by and I thought I wasn’t going to see my kids anymore. That’s when I got really angry. That’s when I went after him.”