In Libra by Don DeLillo, how does he portray Lee's involvement?

In the novel, Libra, Lee defects to Russia only to find it is no more exciting living in a Communist country than living in a democratic one. When he returns to America, he finds himself under the scrutiny of the FBI and CIA. He then teams up with an old acquaintance to attempt to kill Major General Walker, but misses. In the end, DeLillo portrays Lee as someone who is manipulated into taking a few shots at John F. Kennedy as he passes his workplace in a motorcade, as well as a witness to the crime he is accused to be responsible for..... a man who is set up rather than guilty.