In Rasputin Must Die! from the Reign Of Winter Adventure path, we are introduced to Automatic Firearm rules. Of interest to this question are the following lines from the relevant text on Automatic Weapons:
A weapon with the automatic weapon quality fires a burst of bullets with a single pull of the trigger, attacking all creatures in a line. This line starts from any corner of your space and extends to the limit of the weapon’s range or until it strikes a barrier it cannot penetrate.
An automatic weapon cannot fire single bullets that target one creature.
One person could, in theory, have an automatic firearm to which they could apply the Snap Shot feat.
What happens when someone makes an AoO using such a weapon?
As far as I can tell, one person can get a whole line of people to suffer the AOO along with them, but this seems strange. Though I admit that automatic weapons were probably not written with Snap Shot and the like in mind.