According to the clerk, 20-year-old Levi Walker entered the Phillips 66 gas station in the 3200 block of South Keystone Avenue just before midnight and demanded money.
It's still not immediately clear what happened next, but at some point, the clerk pulled out a gun and shot Walker twice.
Walker was able to stagger outside of the business before collapsing from his injuries. He was pronounced dead at the scene.
Customers told RTV6 at the time that the gas station had been robbed before.
“This isn’t the first time they’ve tried to rob him and to be honest with you, I believe he done what he should have done,” said Brian Nordby. “The guy comes in with the intention to hurt him and rob him, that’s self-defense all the way through from what I could tell.”
The incident is one of two fatal shootings that have been ruled self-defense so far this year.
Click the image below to see all of 2017's homicides so far: