it also should be noted that while police don't legally have to protect you, basically all police departments have it as a obligation to protect and serve the people. the police department took the bureaucratic disciplinary measures and fired him. but the legal charges of child neglect and endangerment are actually civilian charges brought up in a civil court by the parkland students. sure, most civilians in that situation couldn't be charged in this situation, but seeing as how the "civilian" was a on duty officer, with training and weapons, was obligated by the police department, and heavily implied by the public. it's not hard to see why he was charged to the fullest extent of the law.
i do understand why you would think he shouldn't be prosecuted seeing as the supreme court ruled that he wasn't obligated to help. but it's kinda the same thing as a solider refusing to participate in combat. all the military can do is discharge him. it's up to a civil case to legally charge them