I believe the dog had been stolen by the crook, which is part of the reason they didn't stop, but also I think it was to try and get the coppers to back off, sort of "Get any closer and I drop the dog out at this speed".
This is a high-speed chase in my hometown of Spartanburg, SC. It's from 2008, but is pretty intense. The suspect is shooting backwards at the Trooper while driving. He got 16 years in prison for this stunt.
Here's one from Florida that is pretty good too. Bumper to bumper traffic and high speed after the suspect hit the Trooper's car during a traffic stop.