Occam's Razor: "All things being equal, the simplest solution tends to be the best one." For example, if 2,950,000 people (2002 figures) are accidentally killed or injured on US highways every year, is it more likely that the governor of New Jersey's injury was the result of an accident or that the other guy specifically targeted him? If an alienated, possibly crazy, person can kill 3 dozen people in Virginia, than why can't an alienated, possibly crazy, person kill a president without the necessity of bringing in the Mafia, LBJ, Castro and unknown additional people?