I was arrested for shoplifting but they fingerprinted me and took my picture!?

They asked me to come down to police headquarters (called me at home and said a store had me on videotape!). So I went down and was given an appearance ticket. But they finger printed me and took my photograph. Isn't that a little premature? Suppose I am innocent? PS: They got my name because I had been at the pharmacy picking up antibiotics while in the store and the manager who saw me on tape SUPPOSEDLY asked the staff "who is this person". They looked up my account and got my home phone. That is how I got caught. But how can they finger print me and take my picture when I haven't even been given a chance to prove my innocence?