Depending on the specifics of the reactor, the dose received by the bathers would likely be high enough to require NRC action, but low enough S/T health effects are unlikely, or entirely statistical.
In the training reactor I worked in a long time ago, I think start-up procedures required visual inspection of the pool, and (I think) arming the external alarm?? People being able to just walk into your reactor room is a big no-no.
I haven't dealt with a reportable incident, but Danny may be facing a year of paperwork. (What happened? Were procedures followed? If not, why? If so, what is wrong with the procedures? etc, etc, etc.) He may need a lawyer.
In the real world, his next step would be to open the three ring binder, and follow instructions. Phone calls, shutdowns, evaluating the scene for possible contamination, etc, etc, etc. Poor Danny.