The Cozumel municipal (city) government has no say in choosing the head of the municipal police; by law, the Mexican military tells the municipal president who it will be and the municipal president has no choice in the matter. The previous head of the municipal police was also a military officer appointed to the municipal position by the military and later removed by the military, just as this new one was and will be.
I don't believe any of the guys assassinated this year saw anything coming either until it was too late. It is just a question of being in the wrong place at the wrong time, whether you are the target or just collateral damage. Several of these shootings were in the Centro area, within a block of the Malecon and not "far off the beaten path" at all.