Friend [subject-が] passed-away [after-てから] exactly one year [subject-が] elapsed.
~てから marks the temporal starting point — 'from the point of passing away.' 経過する (けいかする, 'to elapse') is more formal than 経つ (たつ) for the passage of time. 丁度 (ちょうど, 'exactly') emphasizes the precision of the anniversary.