a book of bunk published by a profiteering hack...the whole theory was disproven by this frame in the Bronson film of the assassination ...the frame is at the instant of the head shot.... the yellow arrow points to the head of the accused Secret Service agent, he is sitting down and not firing his AR-15...plus this frame indicates there would have had to been a whole lot of blind witnesses if they didn't see that happen ...for instance Charles Brehm must have been 5- 10ft away from Agent Hickey when he supposedly accidentally shot his gun (he's the guy in the tan jacket on the curb)
I have read that several claims made in the book have been refuted, but there has been plenty of support for the main hypothesis that one of the wounds, at least, was caused by a .223/5.56 round.