Random questions and stuff.
Is the VIP Bathroom and any other areas locked when the passengers entered the train?
Were there anyone imprisoned in the bathrooms?
Were the crowbar and the gun used in the murder? Were they the only items that have killed someone?
Can you walk across each cart from both floors?
Ivan entered with the passengers. He then immediately proceed to enter the VIP bathroom(if it's not locked) or the overhead compartment on the 2nd cart(if it was locked). As Terry(with a bottle of alcohol) came again with a key to open the bathroom for Richard to use, Ivan assaulted him, taking the bottle and killing him. Pulling Terry to the bathroom, Richard came to look for Terry. Ivan saw him and also killed him for security. Pushing him in, he then locked the door with the key. However, the detective was coming at the time, so he ran to the overhead compartment, leaving the key. Knowing that the detective would return to warn people, he began to go to the 5th cart, taking a bottle of alcohol in the diner cart in order to feign ignorance by making himself drunk in the 5th cart's bathroom.