That makes me sick, both the picture and the OP's description of things. Some people never cease to amaze me with their stupidity and utter lack of regard for anything but themselves on occasion. Obviously that's not everyone that's like that but the ones that are...
It's a long-shot, especially depending on the size of town you live/work in, but sometimes local law enforcement can bring more resources to bear than an individual citizen can. I have the luxury/bane of working for a small town department and our prosecutor is incredible about handling animal abuse/neglect cases, whether individual owners or corporations like that. Sometimes the larger cities have greater resources to bring to bear in situations like that but also a larger case load, thus a catch 22. Sucks all the way around, much like when kids are being abused: sometimes it seems like no one cares except the person trying to right the wrong.
Just a thought but you might try contacting the mall owners as I think you already said you had and notifying them. A blog or otherwise a mass-audience venue might make an impact, as could a petition to bring the situation to light. Also, could you get a part-time job there to get photos? The impact of a picture is incredible as far as making your points. Good luck and my hat's off to you for trying to correct the situation.