Can i be sued for shoplifting even if the police didn't press charges?

I was apprehended shoplifting around 2 months ago at a Metro grocery store. The police came but in the end, they let me off and did not press charges. I was banned from the store and was told if I was caught in there again, I would be arrested and such. However, the store just sent me a letter saying they intend to recover their losses that they incurred. They want me to pay a settlement of a little over $500.00 and if I don't pay it, they will take me to court. I don't know what to really make of it and I don't know if they're just trying to extort me. Is it geniuine? The cops let me off and just gave me a warning not to come back and do it again. Charges weren't even pressed. Can the store really do this?