There is a similar case in France (albeit at a much smaller scale), where DNA tests were run on all male pupils and staff from a school in an effort to find the perpetrator of a rape. So far they haven't found a suspect.

http://www.theguardian.com/world/2014/apr/13/french-school-d...

http://www.theguardian.com/world/2014/may/22/french-school-r...