I'm out at "The Great Place" a couple of times a year. The improved part of the base is huge to begin with and has something like 65,000 permanently stationed personnel. Then you have an immense range that they use for armored and cavalry maneuver training. It really is hard to describe the size of the place.
In addition to the 65k, Fort Hood can support 2 Armored Divisions coming from other places and training concurrently. Also, the Central Test Support Facility is at Fort Hood and you can get a number of contractor personnel testing all of the Army comms and command and control systems. For the ADs, you're looking at anything from 10k - 25k personnel with up to 1,000 tanks, APCs, artillery, helicopters, and then support vehicles.
So, you're looking at a town anywhere from the size of Fort Meyers to Gainesville depending. It's not really surprising that you'd have a bunch of incidents.