"I thought about calling the police," Jill Zarin said of Mario Singer ... He has been working at the brand since 2016, and is the author of the No. 1 New York Times best-selling book, Not ...

Bobby Zarin passed away after a battle with thyroid ... The cancer wound up returning and spread to his lungs. In Fall 2016, Jill revealed to PEOPLE that he was diagnosed with a brain tumor ...