What happened exactly is not clear from sources. What we know is this: Back in early June - as the trial was getting underway - Bulger was being transported back from Boston when his security contingent encountered what a source described as a "major scare." The driver drove frantically onto the Plymouth jail grounds and guards at the facility scrambled and were put on high alert.

On June 14, I drove this route to see how vulnerable it was, and it seemed apparent that law enforcement had reasons for concern.

"Well, it's probably a 45- or 50-mile ride from Boston to Plymouth," said U.S. Marshal John Gibbons. "But I'll tell you, we usually don't discuss our reasons or anything pertaining to security or transportation.

The U.S. Marshals service and the Massachusetts State Police have never spoken publicly about this security scare, and to be clear, they are not speaking publicly about any specific event now. But, in a one-on-one interview with Gibbons, he alluded to such an incident.

"I will say this: Earlier, when we were transporting, there were some things that were out there that raised our eyebrows, raised our attention, and as a result of that, I contacted the State Police," he said. "And we decided to transport Bulger in the fashion that we're doing it now - we're blue lights and sirens from the facility up to Boston to the courthouse and back. Safety and security are the reasons we're doing this."

Each day as Bulger prepared to leave the Seaport the U.S. Marshal service rolled out two SUV’s and 2 easily identifiable State Police vehicles from the rear of the courthouse. With sirens blaring they darted toward Northern avenue.

One of the SUVs was armor plated, but it was up to you to guess which one – and the point, of course, was to confuse anyone up to no good.

"I was a former State Police officer," Gibbons said. "I've been involved in a lot of high-profile trials, violent trials - organized crime and gangs. I just thought this is the way we need to transport him.

At the conclusion of this trial, Bulger, whose safety has been a priority for U.S. Marshals and the State Police, was transported back to Plymouth, safely ensconced in a jail cell.