"The crucial detail is the erasure of the serial numbers. The numbers do not appear to have been physically removed. Instead, the guns seem to have come off the production line without any serial numbers, or they could have been erased with high-tech industrial technology. The lack of serial numbers suggests that the weapons were intended for intelligence operations or terrorist cells with substantial government backing."
These guns are probably from the Mossad or the CIA, or both. What we're seeing in Iraq is a national resistance against the American occupation, a resistance which is directed at the American troops and Iraqi collaborators (which include the Iraqi police). Any civilian deaths or injuries are collateral and accidental. Parallel to the resistance, we also see a concerted action by a major foreign intelligence service or services to create a civil war in Iraq by staging what appear to be sectarian attacks against specific groups in Iraq. These attacks always involve civilians and are always immediately blamed on the resistance. Occasionally these attacks are directed at foreign aid workers, exactly not the kind of people the resistance would be targeting. The attacks against civilians are used by the American authorities as evidence of the illegitimacy of the resistance. The confusion - much of it intentional - in describing what is going on is based on not distinguishing the legitimate resistance from the agents provocateurs.