What is wrong with people??!!

We have a very nice park a couple of miles from here. Those in Vegas probably know it as the "dinosaur park"--the nature discovery park in Aliante. There is a large duckpond with a waterfall, and a huge kids' play area. I try to take Ian to the park several times a week (lately we've been going at 9am because of the extremely hot weather) and today I noticed there didn't seem to be as many ducks as usual. I didn't think much of it, and then as we were leaving, I noticed a posted sign. Apparenly, people have been shooting BLOW DARTS at the ducks! What would possess a person to do that?! We have a nice place to take our children where they can "play" with and feed the ducks and some jerk has to go and ruin it for everyone. It makes me so angry!