Ex-FBI counterintelligence chief Charles McGonigal sentenced to 50 months in prison for working with Russian oligarch

One of the highest-ranking FBI agents to ever face criminal charges was sentenced to over four years in prison on Thursday for secretly colluding with a Russian oligarch.

Charles McGonigal, a former counterintelligence leader in the FBI's New York field office, pleaded guilty to a conspiracy charge. McGonigal's lawyers had asked for no prison time, but the judge came down harshly on the former FBI bigwig.

"I committed a felony and as a former FBI special agent it causes me extreme emotional and physical pain," McGonigal told the judge prior to the imposition of the sentence. "I stand before you today with a deep sense of remorse."