Another legal issue here - the police are obliged to retain ALL evidence and material gathered as a result of the incident at the scene and during the subsequent investigation under what are called 'disclosure rules'. This is a legal obligation of the police so that the defence can review all the materials to make sure that nothing assists their defence case at trial, or undermines the prosecutions case, even if the police didn't use the material in any way.
One to think about, as its another legitimate reason a camera could be seized, and by the book, should be, as if the officer knows you have material on your camera related to the case he should at least review it under disclosure rules. In reality it would be impractical, but if, for whatever reason, you make yourself stand out you will of course get unwanted attention.
I will make it clear I dont agree with it, as some people seem to think I'm defending the officer's actions at this particular scene, but thats the legal issues all officers are faced with at scenes like these.