I have heard it said that in a conspiracy it's not really that the real question is not "Who pulled the trigger?" but "who paid for the bullets?".
In the JFK assassination - even if you believe that Oswald by his lonesome sat up in that 6th floor window with a rifle, watched and did nothing as JFK's limo nearly came to a stop turning left onto Houston street and headed right at him with no obstructions and a very, very easy shot, waited for the limo to make a hairpin turn onto Elm during which he could have almost dropped the rifle and killed JFK with it, waited for the limo to get about 50 feet down Elm until a tree obstructed his view, then fired once, missing, fired again hitting JFK in the back with the bullet going on to hit Gov Connely who didn't react for at least a second and then finally taking one last shot that entered the back of JFK's head at the hairline and exited at the top of his head; even if you believe that Oswald alone did all that, you might want to ask yourself literally "who paid for the bullets"?
Ammunition for a 6.5 Manllicher Carcano rifle was only available at 2 locations in Dallas IIRC and neither sold any ammo to Oswald. The bullets that were alleged to have killed JFK were made by Western-Winchester Cartridge Co. They made only 4 lots of 1 million bullets back in 1954 for the US government. they were meant to supply anti-communist insurgencies around the world and eventually cam back as surplus. The assassination bullets had to have come from one of these 4 lots. How did Oswald get the bullets. It is known that he didn't buy the bullets in Dallas. There is no record of him buying them mail order either. And trust me they looked. So who paid for the bullets?
And while we are at it. Isn't it funny that the money order that was used to purchase the rifle was never stamped as being paid? That's strange. Also strange is the fact that the serial number on that money order came from a stack of money orders where the other money orders in that stack were cashed in sometime in 1964, long AFTER the assassination.
Does this prove a conspiracy? No. But is sure is interesting.
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By the way if you doubt what I said about sitting up on the sixth floor choosing when to shoot I suggest you download the simulation "JFK Reloaded" and give it a try. Try to duplicate Oswald's shooting that day. Then do as I say and try shooting as the limo turns onto Houston Street. Let me know how well each strategy works. Now of course if there were someone down on Elm Street up on the grass knoll then it wouldn't make sense to start shooting on Houston Street.
Coincidence? Who knows. They're all dead by now.