If this was a hired hit, that is one very bad hitman.
No professional hitman is going to incur the risk of shooting someone on a midtown Manhattan street with camera surveillance on every corner. The chances of you getting caught, or at least accurately identified, are nearly 100%. A professional hitman would have chosen a much more isolated location to complete the job.
The gun he used also jammed between each round he fired. A professional hitman is going to make sure his equipment is working properly before going into a hit.
This is far more likely to be a disgruntled man that had some sort of bad experience with United Healthcare. All it takes is one mentally unwell person with nothing to lose that decides exacting moral justice outweighs the benefit of his freedom/life. It's happening more and more frequently.