I’m in Az too and see that open opportunity all the time. Some folks should just not carry open because they have bad habits and open themselves up to others and the ability to take their firearm. Those need to conceal carry for sure.
And the guy was in South Phoenix - probably the worst part of town. I haven't been down there in a few years and have no plans to go back. I doubt much has been done to clean it up. There were like ten things the guy could have done to prevent this, from using a decent holster to driving to the other side of the I-10 for lunch.