1. photograph the event if possible;
2. Write a brief statement about the event and describe as precisely as possible how to arrive to the location (if there is a correct address, some visible object, distinctive sign and the like.)
3. Send a statement together with your photo in writing to the competent Municipal State Attorney's Office, to the municipal services monitoring officer in your city, town, or municipality, contact the police (192) or the association Animal Friends (Prijatelji životinja).

WHOM TO CALL: and/or Green Phone service for your county (072 123 456) - the report may be sent anonymously, too.
NOTE: You can always call the service 112, especially if it is a matter of great urgency, and during the weekends, holidays or at night