Rav Elyashivs Psak is actually written down i Hebrew and published in the Teshuvah Sefer that collects his responsa, He states clearly that there must be reglayim l’davar to allow going to the police as well as further conditions.
If anyone wants further clarification they can talk to Rav Feivel Cohen shlita a Rov in Brooklyn who is a born and bred American as the Responsa is addressed to him and he has spent hours upon hours discussing the issue with Rav Elyashiv shlita.