Frontierland Parade Death: On February 11, 2004, 38-year-old cast member Javier Cruz was crushed and killed by a parade float. Cruz was dressed as Pluto, and as the parade was preparing to go into Frontierland, he caught his foot under the Beauty and the Beast float. Cruz was unable to get out of the way, and the float operator couldn’t stop it in time. His body had to be taken out by forklift, and Disney was hit with a substantial fine by OSHA.
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.