Adding credence to the theory that Brooklyn landlord Menachem Stark was kidnapped and murdered by professionals, a law enforcement source tells the Post that the NYPD found a cell phone attached to the bottom of his car, which could have been used to track his movements. Previously, it was reported that the suspect caught on video was lurking around Williamsburg for weeks. Mayor Bill de Blasio weighed in on the case in a radio interview Saturday night, saying it's a "high priority" for the NYPD. "We will find who did this to him and who robbed children of a father and a wife of a husband,” De Blasio said, adding that he found the Post's "Who didn't want him dead?" cover "not appropriate."