Custodian Falls to His Death: On February 14, 1999, a 65-year-old part-time custodian was killed when he fell off a gondola while cleaning the Fantasyland Skyway station platform. The ride was accidentally turned on by employees who were unaware he was there, and he grabbed a passing gondola in an attempt to get out of the way of an oncoming car. The worker lost his grip, fell 40 feet to his death, landing in a flower bed near the Dumbo ride.
Seriously though I am surprised deaths don't happen more often. The Walt Disney parks had 132,549,000 visitors just in 2013. So just in that year alone the average was more than 37 thousand people per day.
I'll bet you it is statistically safer to play and have fun inside their parks than the trip flying or driving there.