Killer Whales for a reason

Yesterday at Sea World in Orlando, one of the killer whales did just that to a trainer that has been working there for years. I dont understand how these people just get in the water with animals of that size and power. I know the argument is that when you breed them and raise them at such a young age its rare for anything to happen, but anything can and did happen as well. This reminds me of the time that the tiger that does the show with the two guys from Vegas attacked his trainer as well. These things obviously happen so people should be much more cautios and careful.