Nor should they.
The story from the New York Times.
You can read everything I've written about Sean Bell. This post is probably the best, if you just want one.
Also, on principle, I'm against recharging people at the federal level. Smacks of double jeopardy to me. The Fifth Amendment is pretty explicit: "[No person shall] be subject for the same offense to be twice put in jeopardy of life or limb." That's what trying somebody at the federal level is. One crime. One trial. Here's to the Bill of Rights!
Too bad the Supreme Court begs to differ.