In the end he was caught because his van was identified and because "One of his sons had revealed to his then-girlfriend that his father had placed a bomb in Harvey's." I always wonder at how criminals that otherwise might seem movie-like masterminds are caught as a result of mundane mistakes and outright stupid moves like this. You would think if you are going to bomb a place, the first thing would be to not talk ab…
Eventually, the sons of "Big John" caved in to the FBI in interrogation. While the tip of the former girlfriend made the whole family prime suspects in the first place, they did not have anything on them until the sons decided to talk (and get immunity for their involvement in exchange).