Ruby actually fired a blank! Oswald, who had asked to wear a dark sweater before the transfer so he would look better on television, groaned twice and dropped to the ground in an Oscar-worthy performance. The CIA then double-crossed him in the ambulance and shot him for real.

A fatal shot could only be guaranteed if someone else fired it. Absent this precaution, there may well have been a second “magic bullet” to explain: how a single shot by Ruby caused two wounds to Oswald. The evidence that Ruby did not shoot Oswald: photographer Bob Jackson, who took the Pulitzer Prize-winning photograph of the “shooting,” said there was “not a speck of blood anywhere” on the body or at the crime scene; the two “stretcher photos” of Oswald being carried to the ambulance show not only no blood on his sweater, but no damage to a single fiber.

http://educate-yourself.org/cn/jfkassassination23feb12.shtml