There is no statistic or forecast that says today is 9/5/12, LEOs have an 54% chance of being killed in the line of duty today. It is a competitive line of work to get into.
EDIT: there is no given likely hood, the chances of you dying depends on each different stop, call, or scenario. You could pull over a bunch tough looking guys and they could be the friendliest people you meet. On the other hand, you could get gunned down by a innocent acting single mother who calls you because her ex husband beat her again, then when you try to take her ex-husband to jail, she guns you down.
That's why some people get into law enforcement (not the risk of dying part). It's about having a natural sense of curiosity and wanting to investigate things. Also, It has to do with going into work each day, knowing that it's going to be different than yesterday, and you get to do what you want (to a point).
You can't read into all the officer involved shootings and deaths and let that drive you away from wanting to get into law enforcement. If you get a job and worry about getting shot at all the time, you will be in for many years of unhappiness and stress can cause diseases. However, on the flip side, you need to be vigilante enough to know what your doing is dangerous and you need to be ready for the **** to hit the fan and react in seconds.
And what Les S said about watching to much TV and believing that's the real thing, you can't believe any of that because you wouldn't last long.