 Author Francis Wilson , 11 years old at the time of Lincoln 's assassination , wrote an epitaph of Booth in his 1929 book John Wilkes Booth : " In the terrible deed he committed , he was actuated by no thought of monetary gain , but by a self @-@ sacrificing , albeit wholly fanatical devotion to a cause he thought supreme . " Others have seen less unselfish motives such as shame , ambition , and sibling rivalry for achievement and fame . 
