I would think that unlawfully killing a uniformed federal employee in the course of his official duties (in this case driving a marked government vehicle) should be a federal crime, in addition to a state crime. Anyone out there know if it is?.
FWIW the Bureau of Labor doesn’t classify USPS employees as federal employees. That may be the “loophole” on the crime.
This says it is;
https://www.venzalaw.com/blog/2019/april/attacking-a-postal-worker-can-have-serious-conse/