The dumb thing about these posts on social media claiming to be the bomber or his brother is that the bomber is a terrorist and as such the 3 letter agencies can spy and share that data with law enforcement.
I was reading how they captured this guy. They could not identify his pic at the FedEx drop. but they listed all cell phones on in that radius of the FedEx location (12 miles???). Matched up the names, apparently he was being watched or wanted from something else and became a target. Apparently found his location through his phone. Pretty simple.