The story you refer to appears to be a hoax. It caught me off guard too. To amend matters Bill Hamilton, who was behind the original posting, sent a new message to rense.com, part of which reads:

From Bill Hamilton skywatcher22@hotmail.com

I received a newsletter that evidently had factual news stories bundled with a bogus news story. The factual news story was simply a report on the disclosure press conference.

The bogus news story was on the JFK speech notes regarding his alleged disclosure on ETs. The professor cited in the article, Lawrence Merrick, may not exist at all as no reference can be found in a search.

I did a search from several angles and found the source of this bogus story:

Weekly World News newspaper (Canada) Date: April 30th, 1996

JFK WAS SHOT TO PREVENT HIM FROM REVEALING TRUTH ABOUT UFOs!

The Weekly World news is notorious for printing bogus stories.
Sorry about that, but thought I had better make amends as it caught me off guard.

Another story was circulated a while ago on some guys that were given evidence in a contact with ETs. This is generally not the case with contact reports so this was out of character for such stories.

I am afraid that we are bombarded with all sorts of stories on the internet that we do not have the time to check out but still must somehow find the time or relegate such tales to online urban legends.