Changes were made behind police chief’s back

Demotions aren't usually discipline unless you have a merit system that says you can't be demoted from a particular rank without good cause and hearings. Majors and above on LMPD can be demoted without cause to Lt. Small departments can do the same, down to the merit rank they had, which depends on what's been put in city ordinances, rules or contracts. Some would prefer to retire than be demoted. If you're hired in without a merit rank, then they can fire you for anything, including not being compatible with the Mayor.