Maxine Hepworth-Taylor knows little, yet, about how her nephew died. But she knows how he lived. ''He was such a good, good kid,'' she says. ''He was a Granite High School student, he was an Eagle Scout . . .''
   
    ''. . . he was my Lex.''
   
    Lex S. Nelson, a 21-year-old Army specialist, was killed Monday near Tiqrit, Iraq, when he fell from a guard tower.
   
    Nelson, assigned to the 1st Battalion, 41st Field Artillery, 1st Brigade, 3rd Infantry Division, in Fort Stewart, Ga., was just weeks from returning to the United States after serving a year-long tour in Iraq.
   
    The 12th of 15 children, he had last communicated with his father, Ellis Nelson, also a Bountiful resident, in an e-mail one week before his death.
   
    "I'm leaving on a convoy the 29th of December. I'll probably be back in the U.S. on the 2nd of January," he wrote. "All things considered, life is grand."