"The alleged offender shot him as well. He shot at his head, but the guy put his arm up and it hit there instead," Mr Scott told the Herald.
"He [the offender] took off but was tripped by a customer, and he dropped the gun."
The wife called 111 and police were in the area so managed to get to the scene almost immediately.
The alleged offender was apprehended soon after and will appear in the Waitakere District Court today on various charges relating to the incident.
Police recovered all of the cash taken from the shop and returned it to the couple.
Neither were seriously injured, but suffered painful welts where the slug gun pellets hit their skin.