[PhilDragoo]

The FBI seems to like to target vulnerable innocents: [1]Richard Jewel, [2] the "person of interest" in the anthrax business, [3] Colleen Rowley the too-energetic agent--and whistleblower.

The comma makes the clause independent.

Three distinct vulnerable innocents targeted by the FBI.

Hatfill is the "person of interest".

[concretebob]

You're right, my bad.
I tend to ignore commas in certain places within the sentence.
I have a boss who hates commas, and I've had to learn to write technical reports with out them.
Not being critical, but I would have re-structured the sentence, and placed "the person of interest" phrase at the end.
That's the kind of critiqueing I get every day.
A semi-colon would have served the same purpose.