The legal team for George Zimmerman, who is charged with second-degree murder in the killing of Trayvon Martin, has released Mr. Zimmerman's written statement and several audio and video interviews with investigators, in which Mr. Zimmerman says he was ambushed and then pummeled so violently by Mr. Martin that his head “felt like it was going explode” and that the teenager had covered his nose and mouth before reaching for Mr. Zimmerman’s firearm.