Unexpectedly!

This thread pointed me to this NRA-ILA alert which quoted to this CBS News item:

DEA accidentally finds guns from BATFE operation

Sources say DEA accidentally came upon the guns while stopping suspects in an unrelated case in the Phoenix area on April 13th. When agents stopped at least two suspects, they found two giant garbage cans full of dozens of AK-47 type weapons wrapped in cellophane. Sources tell CBS News that a trace on the first weapon showed it was purchased in Nov. 2009 by a suspect in ATF's Fast and Furious case.