The alleged robber grabbed Ibarra's cell phone and cash and began walking away, police said. But the man stopped to pick up some money that had fallen out of the wallet.
Ibarra, who has a concealed handgun permit, pulled out a revolver and shot the man at least three times, police said. The man was pronounced dead at the scene.
Ibarra was not charged in the fatal shooting. The case will be referred to a Harris County grand jury, police said.
