A happy ending would have been the robber laying on the ground bleeding out. I am so tired of this shit.
I'm pretty sure he was hit a few times, and was running on pure adrenaline. Short of a spinal or brain hit, that can get someone down the sidewalk a little ways.
I have seen a deer run close to 100 yards after being shot with a 12 Ga. rifled slug, and upon field dressing it, found the heart to be in three pieces. That flight instinct is powerful.