The Good Samaritan laws protect the average person for providing a service in good faith in an attempt to save that persons life. If the person administering the aid is a trained professional, such as a doctor, nurse, EMT, etc. they are usually not protected by the Good Samaritan Laws. If you stand by idle and do nothing, there is no possible criminal prosecution that I know of. I don't believe that you are obligated under any circumstances to offer aid just because you are there.