Glad you posted this. I was wondering the same thing. One of Fast and Furious grenades?
[Mexico:]Grenade attacks throughout Tamaulipas; shootouts reported
http://www.freerepublic.com/focus/f-news/2784853/posts
Fast & Furious: Congress expanding probe to include grenades http://www.freerepublic.com/focus/f-news/2784645/posts
[Mexico:]Four reported wounded in Reynosa grenade attack
http://www.freerepublic.com/tag/grenades/index?tab=articles
[South Texas]Border Patrol finds rocket launcher, grenade launcher, explosives near Rio Grande
http://www.freerepublic.com/focus/f-news/2778486/posts
No.
F&F was predicated on standard straw purchase from legal civilian dealers. Grenades would be nigh unto impossible with lots of very deliberate & unusual paperwork, adding $200 to the cost of each one sold.
Yes it is technically/legally/logistically possible to make that scenario happen, but falls into the “ain’t happenin’” category. Would take a special level of genius sociopath to take F&F there.