No conspiracy required to do what Oswald did.
Then why is there so much deception and so many falsehoods in the testimonies of the TSBD employees, particularly and tellingly, of those working on the sixth floor. It should have been so straight-forward, another day at the office, so to speak. Everyone shows up to work not knowing that one of them has murder on their mind, the shots ring out and people are questioned as to where they were and what they were doing at that time. Of course there will be minor discrepancies over some details, that's human nature, but what we see in these testimonies is a complex of misdirection and obfuscation. People are lying (IMHO) and to not ask why they are is unacceptable.
I agree, it takes just one man to take the shots but it takes more than one to create the labyrinth of confusion that follows.