What was the evidence against Jack Ruby?

He shot Oswald in full view of numerous law enforcement officers who immediately placed him under arrest and secured the murder weapon from his possession. The evidence would be to (1)recover the bullet from Oswald's body; (2)have a firearms examiner fire a round from the gun taken from Ruby and compare it to the bullet from Oswald's body: (3) have law enforcement officers attest to their observation of Ruby shooting Oswald, and recovering the weapon from him. That should pretty much make the case. Also, it happened on a live television broadcast so millions saw this event as it occurred.