Can a professor shout at a student?
Under normal circumstances, faculty should never yell or shout at a student. However, faculty are also human beings, and there is always the possibility that under emotional strain, they can lash out at a student. 

I will admit to having been guilty of this once as an advisor, when a student came into my office for a discussion about his research, and made some statements that betrayed a total lack of awareness of what he was doing (and this was a "veteran" graduate student who should have known better).

In the context of teaching, students have reason to expect that the faculty member should not shout at them. However, it is unreasonable to expect that any disciplinary action would be taken against a faculty member for a single infraction.