So, how often does underage driving, with an adult supervising, result in a shootout with the DEA??
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".