If the mayor is corrupt, I would imagine the officer feared some kind of retribution. A rational fear, imo.
Even here in the States, bucking the Establishment often leads to undesirable consequences.
To me its pretty clear the goal of the Left in all of this is to turn all the residents of Puerto Rico into refugees and have them flee the island for Florida in order to vote there and hand the Dems the Presidency in 2020. It's cold-blooded murder and criminal obstruction through denial of relief, but thats the game plan.
Given what we know about the Left, it's impossible to think that there can't possibly be a grain of truth in that theory -- the "refugee" part, at least. I know I saw a version of the Florida-voter angle in the first couple of days.