"I do not believe it was your patronuses that made any effect, honestly," Robert said. "Demons are far older than patronuses. They are as old as creation itself and completely immortal. Entirely beyond most of the magic we know. I will return. I must investigate what we have here. Once you have the students settled, stay in those cars until I return."
He walked the length of the train, seeing students physically and emotionally shaken, but clearly glad to see an adult present. Robert gave many of them reassurances as he moved through the train, checking anything he could see as he went.
He entered the final passenger car. He could see the mayhem and destruction. Clearly most of the carnage had been cleaned up already. He could see the body of an older female on the floor. She appeared to be in one piece. He investigated the car thoroughly, missing nothing. He found scraps of clothing and enough evidence to figure out that the student was a young male. He sighed heavily. The young man had never stood a chance. He found the young man's wand and confiscated it. He gathered as much evidence as he could and collected it into the leather shoulder bag he carried. Once there was no more to be learned, he magically cleaned up the scene himself.
He levitated the trolley woman, as he had learned from his investigation, and put her in the last, empty compartment. Well, clearly there were 3 dead. The student, the trolley woman, and the engineer. His mind began evaluating the evidence he had gathered so far. He still wanted to examine the last fatality, who he presumed had fallen dead at his post in the train's engine. He secured the car, checked the baggage cars completely, and found them untouched. Then he made his way back towards the engine again.
Robert entered the train engine and found Rob at the helm of the train, and he apparently had either figured out the spell that bewitched the thing or had figured out the controls. He looked at the floor and found the engineer's body being used, in a not too classy way, as a pillow for Eli.
"Oh, for crying out loud," Robert sighed. "Rob, get that body out of here. Take him to the last passenger car and secure him with the trolley lady in the last compartment on the right." Robert looked at the young man for a moment, cast a rather mischievious look at Rob, and, knowing what truly yanked Eli's chain, he took the young man's wand first and then cast a spell on his own voice to imitate the voice of Viktor Krum.
"Elijah Nathaniel Krum! On your feet! Now!' He shouted in Viktor's thick accent, right into the boy's ear.