The contractor in question is Harold Thomas Martin III, 51, of Glen Burnie, MD according to authorities. He was charged (PDF) on August 29th with theft of government property and unauthorized removal and retention of classified materials by a government employee or contractor. If convicted, he faces up to 11 years in federal prison.
Authorities raided Martin's house back in August, shortly before arresting him and discovered both physical documents and digital files containing highly classified information. Officials also recovered materials from his car and a pair of storage sheds located on his property. There's no word yet on what source code, exactly was stolen but the fact that the Shadow Broker story dropped right around the same time that the FBI began investigating Martin is an interesting coincidence, while the Wall Street Journal indicated this arrest stems from a probe into that incident.