NEW: Harrowing video shows a gunman opening fire outside an Idaho In-N-Out Burger during a mass shooting that left three people dead and seven others wounded.

NEW: Harrowing video shows a gunman opening fire outside an Idaho In-N-Out Burger during a mass shooting that left three people dead and seven others wounded. The man who recorded the footage says he witnessed the shooter firing into a nearby vehicle "aimlessly without control." Police have identi…