(Covers information from the D.C. comics)
Jesse was a highly-adept computer hacker with an anarchistic mindset. At one point around 1998, he hacked into the NORAD system and almost brought about the nuclear holocaust. He was given a choice after being caught. He could either serve out a life sentence, or join the newly formed S.T.A.R.S. Charlie Team. By this time, however, he was already in contact with the Umbrella Corporation, who sought to remove this new threat to their business.
Jesse's actions in preventing Charlie Team's Mexican investigations earned Falcon's suspicions of him being a traitor, albeit an incompetent one. His identity was confirmed in the Arctic just before being killed by a teammate infected with the X-Virus.