Been in your shoes, first of all, I say always call the cops , even if it seems minor let the cop tell you that and he'll still have to do a report. No report, it's 50/50 in a parking lot, since you were honest and sincere and he a dishonest jackass tell him your damages are $2000 and you will pay for your own car and he pay for his own. Don't feel guilty and carry on, he was probably sitting there waiting for you to hit him so he can scam you,he probably doesn't even have a job!