Who said there is was any running involved. I don't think running should be against the law anyway. The robber ran. You got to run faster than 1300 fps though.
Again, from the original article:
"Once he took off with the money in the parking lot, reports indicate Canul, who has a concealed weapon permit, pulled out a gun and allegedly shot Abbot in the head. Abbot died at the Logan County Medical Center."
When it's reported that 'he took off', that means he's runnin'...