Not often, obviously; however, such a question is irrelevant. In addition, I contest the term "shootout". The term "shootout" implies that both sides:
a) the girl and her uncle
b) the agents
had firearms.
This was a shooting; not a shootout.
Lastly, I wouldn't say that the girl and uncle were under-advantaged (from a self-defense perspective). The girl and the uncle had a car at their disposal, which can just as easily be used as a deadly weapon, if used "effectively".
Irrelevant my butt. You made the claim of:
If you go to the root of the problem, the girl shouldn't have been behind the wheel, in the first place. If this were the case, this never would have happened.
This directly says that none of this would have happened if an underage driver hadn't been driving. So, since altercations with the DEA rarely happen due to an underage driver, your claim that the fact an underage driver was the root of this problem is, well, ludicrous.