I was backing out of a parking space and the person behind me proceeded and i backed into the side of his front bumper He didnt see me and i didn't see him who is at fault?

Any driver that is the backing vehicle has a greater and duty and care to maintain proper lookout at all times. The driver that was traveling on the throughfare has control of the lane of travel and the backing vehicle must yield to them. Infortunately, you would the proximate cause of the accident for improper backing.