We are spiritually bound to generally not discuss your confession. In some places, the law requires reporting if one confesses to harming a minor (or planning on harming a minor, in some cases); in other places, a confession of potential imminent harm would also require reporting. This does not mean that a priest will divulge this information (I don't exactly poll how many "conscientious objectors" there are to mandatory reporting laws). If something said to him in confession weighs upon his soul, a priest may say something to his father confessor without the names/identities attached, for guidance and assistance with the situation.
Usually, in cases where a very serious crime is confessed, the priest includes "turning yourself in" as part of the penance, rather than divulging the information to the authorities himself.
Of course, I also will re-affirm what rakovsky said: it is best to confess to a priest/hierarch/monk that you trust.