My sources tell me that Mayo pushed her to the deck to protect her and to get at the assailaint, who then shot Mayo.
Mayo acted herocially here. He was not on duty on the ship, the USS Mahan, but saw what was occurring in his role with base security/watch, and came to the scene.
IMHO, the guy should ultimately have a vessel named after him. His is much more deserving than somone like Ceasar Chavez or John Murtha.
This nation mourns the loss of this young sailor, a true hero in every sense of the word.