Investigators on Monday were trying to determine what led a 24-year-old man to open fire at an Idaho fast-food restaurant over the weekend, in an attack that left three people dead and seven others...

An armed citizen and off-duty trooper returned fire at the Twin Falls In-N-Out Burger gunman, who was reportedly shocked by the armed response.

Investigators are trying to determine what led a 24-year-old man to open fire at an Idaho fast-food restaurant over the weekend, in an attack that left three people dead and seven others wounded before authorities say he killed himself.