Alright, I found it. I found exactly what I was looking for concerning the mental programming of Jack Ruby. It's from Hidden Mysteries dot org website, and I don't know who wrote it.
Let us start with Jack Ruby who shot Lee Harvey Oswald. After the assassination, when he was visited by members of the Warren Commission, Ruby was completely PSYCHOTIC. Even close friends have testified to this. He kept talking about the Jews, the Holocaust and the new government secretly taking over the United States. The Warren Commission found him not credible. Ruby also admitted that before the assassination he had taken more than 30 (thirty) amphetamines and diet pills. (Preludin and Dexedrine) "They stimulate you !" He later testified. That's right, they induce an artificial model psychosis and its not clear who had advised Ruby to take these. Before the Warren Commission, Jack Ruby testified about a conversation he had on the night before he shot Oswald with Dallas Police Officer Lt. Olson who told him that "Oswald should be cut inch by inch into ribbons!" and praised Ruby as "The greatest guy in the world!"
Ruby's lawyer (Tonahill) believes that prior to the shooting, Ruby had numerous conversations like these about which he refused to testify as these might be construed as premeditation which could have made Jack Ruby a candidate for the death penalty. Can we read between the lines here and decipher the covert methodologies involved ? First Ruby's model psychosis is induced under the guise of dieting pills which are amphetamines. Once the psychosis has taken a noticeable effect he is literally being psyched up by various members of the Dallas Police, government, etcetera, who suggest to him that Oswald should be shot. At this stage, because of the Psychosis, Ruby was unable to see through the trick and the covert manipulation he was being subjected to. To sum up, in 1963 Ruby's model psychosis was induced via an overintoxication of amphetamines and "diet pills". The assassination of Lee Harvey Oswald was then induced by psyching him up via the innocuous "conversations" he later reported to the Warren Commission.
But, think about it. If you were grooming this psychotic guy to shoot someone, would you be willing to be tethered to the victim, who was a skinny guy at that? Would you want to be in the line of fire of this psychotic nut with the only thing between his gun and you being the skinny frame of Lee Harvey Oswald?
If you accept this guy's premise that the Dallas Police provoked Ruby to take action against Oswald, why would you expect them to have any faith with Ruby's shooting ability? Stop thinking that it was a sure thing that couldn't go wrong. It could go plenty wrong. Did I mention that Ruby was psychotic?
That's why the above scenario should be tweaked to say that they planted the idea in his head to shoot Oswald, but, they didn't need him to actually do it. They only needed him to take the blame for it. They could get it done themselves. They didn't need him for that. And they would never have trusted him to do it.
I am telling you the truth when I say that Jack Ruby was not the garage shooter. He wasn't even in the garage at the time. He was already up on the 5th floor being processed. They didn't need him to shoot Oswald. They just needed him to believe that he did, to not dispute that he did.