For one thing O'Reilly says that Booth and his Girlfriend, (prospective wife) were involved in a love triangle as the Girlfriend was also see a young Union Officer by the name of Robert Todd Lincoln. And the Booth's attack on Lincoln at Ford's Theater was not his first attempt. It appears that Booth attempted to attack Lincoln during Lincoln's 2nd inaugural address. That Booth had obtained a position very close to Lincoln while Lincoln was making this address and that Booth lunged at Lincoln but was stopped by a Washington City Marshall who knew who Booth was and let him go passing of the incident as Booth simply loosing his balance.
This is interesting as otherwise unknown History. And does not mean that there was not a conspiracy with other operatives to carry out Lincoln's and other members of his cabinets assassination. But once O'Reilly's claims are critically examined they may give a new insight into the motives for Lincoln's death. And that they may have been as much personal as political.
I know that yes it is Bill O'Reilly. But he was a university history professor at one time.