Yes you can barely make it out in that picture but that is the flag I saw.
Puerto Rico has nothing to do with it. This is a horribly common thing - there was the guy in California a couple of years ago who kidnapped a teenager and held her as a sex slave for nearly 15 years, the people in Germany and England who kidnapped girls and held them (killing some).
The things they had in common were that most of them were married and were helped by their wives (apparently Ariel Castro is married) and that the police blew it on every visit because the kidnappers were “upstanding citizens.” Ariel was a schoolbus driver and the others were all employed and the police wrote off the neighbors’ reports as hysteria or maliciousness.