Detective Tall Nut: Conspiracy on the Rails

It is said that when Gao Nut and Dave were riding the express train to the modern world, they met the big star Dance King Zombie, along with three of his classmates and a dance partner. However, halfway through the train, the Sleigh Zombie suddenly died tragically in carriage No. 5. There was a marked photo beside him. A short time later, all three Dance Kings died tragically in the box, with the same photo around them. The suspect was identified among 10 people. Who was the murderer?