Tomorrowland Stabbing: Long days in the hot sun, combined with drinking and long lines can make people cranky. Sometimes, this goes horribly wrong, as it did on March 7, 1981, when an 18-year-old man was fatally stabbed during a fight. It was after the victim supposedly pinched the assailant’s girlfriend in Tomorrowland, and the victim’s family sued the park for $60 million. A jury found the park negligent for not summoning outside medical help and awarded the family $600,000.
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.