It could be a cell phone pouch.
When the cops pulled up, they could not see any firearm either as it was on the side away from them.
Of course someone had called in a MWAG on him which could be anything. It could be an extreme Hoplophobe. It could be someone that had a vendetta against this man. It could have been for any number of reasons.
But, for the cops to automatically assume someone walking down the street with a black case visible under their shirt is a criminal and should be proned out is wrong.