There's a reason why the three sports of triathlon take place in the order that they do (at least in my mind). To me, that reason is that swimming would be extremely unsafe if it were the last event. Unfortunately, even with the swim portion being the first event, it can still be quite dangerous, and the recent New York City Triathlon is a prime example of that.
I wasn't at this race, so I won't even begin to speculate on what happened. According to this article, there were 28 participants removed from the swim portion of this race, and now it is reported that two of them have died. To me, 28 people needing assistance during the swim is probably not all that high of a number. And with the chaos that takes place during the swim, I'm actually surprised that there aren't more death. Unfortunately there were two deaths resulting from this race.