Looking for information on Reidar Rudmogen/Rumagen

Could anyone help me with information about a man named Reidar RUDMOGEN og RUMAGEN All I know is that he arrived 28 dec 1912 in New York. He was 15 years old, born in Kongsberg. He arrived with a ship called Majestetic who came from Southampton. He traveled alone, maybe he changed his surname. Have found a name in USA: Etta Rumagen and a family name related to her named MANGRUM I am thankful for all types of data.