I can kind of see this. If the FBI or police found a letter on the body proclaiming jihad they probably wouldn't tell the family that right away. They would play dumb at first asking questions about a possible motive just to see what the family knew. And after a few days the media had already run with the anti-gun angle and maybe the police weren't ready just yet to confirm that story to the media either. It would be interesting if someone from the media would follow up with this now and confirm the story (doubt that will happen).
See #102. They already did. The shooting happened on February 24th, 1997. The entire text of the letter carried by Kamal was published in the New York Times only two days later.
The problem with this thread and the one on Little Green Footballs is that everyone is believing article from a Gaza newspaper.