They were in violation of a department policy against taking personal photographs at fires. In this case, it's pretty obvious that doing so was not interfering with the performance of their duties, but that's irrelevant. They still violated a rule which was established for good reason.

Having said that, it's still a very minor rule infraction and the publicity it seems to have received is way out of proportion. It's not something that merits a suspension or even a reprimand. It merits having a superior explain to them exactly why they aren't supposed to take personal photos at fires. No more, no less.