Praise be to Allaah.
There is nothing wrong with this kind of work, because it is taking pictures that serve a purpose, indeed they are necessary. There is nothing wrong if pictures taken at the scene of the accident include people who are not involved. But if the pictures are taken by someone using his own camera, in order to keep the pictures for himself, then this is not allowed. It is haraam not in and of itself, but because of the purpose, which is to keep the pictures for himself with no need to do so. The reason why you are taking the pictures, on the other hand, is for a legitimate and necessary purpose.