Earlier this month we learned the name of a second person who stole top secret documents from the US National Security Agency (NSA). After Edward Snowden admitted doing so publicly in June 2013, the FBI has now arrested the 51-year old Harold T. Martin III at his home in Maryland.
Martin hoarded lots of classified documents, not only from NSA but also from a number of other military and intelligence agencies. The FBI is still comparing them with those from the recent Shadow Brokers leak and a range of other NSA leaks from the past few years, but given what's known now, it seems likely that at least one other leaker is still at large.
The New York Times reported that when the FBI raided Martin's house on August 27, they found paper documents and many terabytes of highly classified information, even going back the 1990s. At least six documents were from 2014. It was reported that Martin first took the classified documents on paper, later on CDs and more recently on thumb drives.
The reason why Harold Martin brought home and stored such large numbers of top secret documents isn't yet clarified. One suggestion is that he may have used them for research for his dissertation about "new methods for remote analysis of heterogeneous & cloud computing architectures", which he was working on at the University of Maryland.