Suspects in the Boston Marathon bombing April 15 in handout photo released on the FBI website, April 18, 2013. REUTERS/FBI/Handout

When the Russian security service in 2011 asked the FBI to check up on Tamerlan Tsarnaev – one of two brothers now suspected in the Boston Marathon bombing – the request would have come as no surprise to a quiet, former FBI special agent in northern California.

Michael di Pretoro had been sent to Moscow in 1994 as the FBI’s first legal attaché, or “legat,” in Russia. He had a daunting task: to establish formal cooperation between the FBI and the Russian police and security services.

The bureau’s hope was that a successful liaison arrangement would help both countries fight Russian organized crime. “There was the issue of loose nukes,” di Pretoro said. “One of my biggest fears was someone would get one of these nuclear weapons and it would cause a catastrophe in the U.S.”

The ex-FBI agent, who now runs his own international consulting business, first persuaded the Russian MVD, which handled criminal investigations, to sign on to the liaison arrangement. Minutes after officially setting up the new office, di Pretoro got a call from the Russian Federal Security Service (FSB) the agency responsible for counterterrorism and counterintelligence.