A shotgun loaded with rocksalt shells isn’t going to hurt people or infrastructure, but it’ll kill fragile pigeons dead.
Also, presumably the people you hire to shoot pigeons would be doing so on rooftops and in places where the pigeons nest, not just blasting flocks in the park or in the middle of the street. Also, presumably the people you hire to shoot pigeons would not be shooting if people are in front of their guns. 
