yemeni government knows about what happened after the attack but the security agency maintains some militants were killed in the strikes. drone strikes are less frequent than they used to be now. nor are claims or documented reports that drone strikes killed civilians instead of their targets. none of that is new. what is new here, what we're learning tonight is this. usual officials have told nbc news national investigative correspondent michael isikoff they launched an internal investigation into this strike that we just showed you that footage from. that is news. it seems like it could be important news. watch this from michael isikoff. >> drones have become america's weapon of choice against terrorists enclaves overseas. this exclusive video showing bodies of victims of a pentagon drone strike on the 12th was taken by a yemeni journalist and given to nbc news by reprieve, a rights group.