Is it illegal to post his picture on the internet?

[Positive]

The store I work for was robbed at gun point last week. I had to spend all day with the police giving them a description of him because he knew where all of our security cameras were and we ended up only getting bad side profiles or just his body. I found out that he's on crimestoppers. He's robbed several stores at gun point so I went home and spread security pictures from previous robberies where you can clearly see his face. I put it all over my facebook, twitter, everything. I want this guy caught. He scared everyone. Today, I came into work and a customer called and told us she was going to alert authorities that one of our employees had posted it, that it was illegal to post his picture.

So, in summary, the guy robbed my store, I put his picture on the internet to try and get him caught, and a customer is going to authorities over it. Is it illegal to post a criminals picture on the internet when no one knows his name?

Plus, why would she be so upset that I posted his picture unless she knew him? Who is like "OMG HOW DARE YOU TRY TO CATCH A CRIMINAL?"

I just don't get it.....