Marco Díaz-Muñoz, whose class was the first attacked, says the gunman looked like a robot as he killed and wounded Michigan State students

The noise was so loud it didn’t sound like the gunfire from the movies to Marco Díaz-Muñoz — it was more like an electrical generator blowing up. “But then there was one, there was two, there was three,” the assistant Michigan State University professor told CNN of the sounds. And then a gunman stepped inside his classroom.