I'm not in charge of police policy (of course) but if I was, this would be the new policy for routine traffic stops in Chicago:
1. 4 officers to a vehicle, 2 carrying AR-15 rifles.
2. Upon traffic stop, 2 officers immediately exit vehicle and "cover" the stopped vehicle and advance to a viewpoint where their presence (and aimed rifles) is visible to vehicle occupants.
3. Once vehicle is "secured" in this manner, remaining two officers approach vehicle (on both sides) with service weapons drawn to obtain license and info.
I believe such tactics might discourage shootings such as this one...