If the officer is exonerated, he should and will sue the Department for termination and hopefully, attorney fees. The Department appears to be was waaay too hasty in its decision.
Do you know what the penalty is for planting evidence, State then Federal?
Even if I thought he gunned the guy down in cold blood, as an executive in the department I would oppose any effort to terminate him that quickly. There is a process for determining qualified immunity and they didn’t take long enough to determine that. You are already getting sued by the family, why add the terminated employee?