I guess we could call Gunwalker "The Give That Keeps On Giving"

if it weren't for all the bodies involved:
A third gun linked to “Operation Fast and Furious” was found at the murder scene of Border Patrol Agent Brian Terry, new documents obtained exclusively by Fox News suggest, contradicting earlier assertions by federal agencies that police found only two weapons tied to the federal government’s now infamous gun interdiction scandal.
...
Unlike the two AK-style assault weapons found at the scene, the third weapon could more easily be linked to the informant. To prevent that from happening, sources say, the third gun “disappeared.”
Like the whole mess would have 'disappeared' if some agents who actually ARE lawmen hadn't decided to blow this whistle on this.

Oh, remember the information about Gunwalker appearing to be operating in Texas as well as Arizona? And Grenadewalker?
Another plausible motive for hiding the weapon is that it would be traced to a different ATF operational sector, as an early indication that gunwalking was not limited to Operation Fast and Furious in the Phoenix Field Operations area. We now know as a matter of fact that all three federal agents shot with walked firearms had weapons walked from Texas recovered at their crime scenes. Immigration and Customs Enforcement (ICE) Agents Jaime Zapata and Victor Avila were ambushed in Mexico by members of the Zetas cartel, including at least one armed with a weapon from Lancaster, Texas, the Dallas Field Operations area.

The SKS “disappeared” by the FBI from the scene of Agent Terry’s murder most likely came from Dallas, but could have come from what appears to be a second Texas-based gunwalking operation, suggested by considerable circumstantial evidence to be centered in the Houston Field Operations area.

The fact that every U.S. agent gunned down in the line of duty was fired upon with weapons recovered from apparent gunwalking operations in the Dallas and/or Houston Field Operations areas — not to mention the revelation of an domestic gunwalking operation in Indiana dubbed “Gangwalker,” and now “Grenadewalker” — suggests a widespread program to arm violent felons.