??? 5 Points to anyone who can correctly answer this Question???

One fine morning a father and his son take a walk. Just when they were about to turn back home a car suddenly appear on the crossroad and hit the boy, seriously injured. The father carry his son, run all the way to the nearest hospital and rush him to the Emergency Room. The doctor quickly came, did a thorough check on the boy and finally say to the father, "Though I'm the only Doctor available now and even though the boy need immediate operation, i can't operate him because he is my son." Who is the Doctor ?