It sounds like no police officers were fired as a result of this investigation.
21 maimed or killed.
I really think this is more than a little bit of middle of the night speeding.
That said, I don't think that actions outside of work necessarily should mean someone is fired. Using your badge to attempt to get out of trouble, or stating that you feel that speeding is your 'right' (on-duty or off-duty) just because you are a cop, on the other hand...
http://www.sun-sentinel.com/news/local/speeding-cops/fl-gx-f...
120 MPH was almost double the speed limit (65 MPH) and as the data shows it was a routine. The data shows only average times, so who knows what his top speed was (he was "only" averaging 95 the day he got busted for going 120).
He was very frequently averaging speeds that constitute reckless driving. He's lucky he just got fired, his license should be suspended for a long period of time just like it would be for anyone else that wasn't a cop.