The San Diego Unified School District, like most large school districts, universities, even transit systems, in the US has its own police force - this is going to a police department... they have 54 officers, so its larger than many small town departments by a good stretch.

Also, whether there's a military presence in the area or not is irrelevant to their needs - the military doesn't provide tactical support in law enforcement actions.

I'm not taking the position that it's a sane use of resources or a necessity (I don't think it is)...