Source: dailymail.co.uk
An informant identified Dallas plice officer J.D. Tippit as the killer of John F. Kennedy. This is the police officer that was killed by Lee Harvey Oswald. The informant said that the information came from individuals previously active in the Fair Play for Cuba Committee. The note alleges that a week before the assassination Tippit and someone (possible Oswald) met at Jack Ruby's nightclub. Tippit was allegedly head of the John Birch Society in Dallas.
Source: dailymail.co.uk
So it wasn't Lee Harvey Oswald???? :-)
There are some many theories, it's hard to say. That is why I for one was awaiting the release of the documents.