The Witch's Game 4

[Kuroaitou]

The murderer tampered with the alert system.

The system malfunctioned.

The murderer gagged the victims and proceeded to asphyxiate them.

The culprit had no way of accessing the alert system on the train.

The alert system would not malfunction.

No one was gagged.

And how would he gag them anyway? >_>

[CrockettRocket]

Probably with the pillow.

[Submachine]

Sorted things out a bit. Take 2.

Opening the door:

Spoiler for Hidden:

The door to the driver's cart requires a conductor's key to enter.

The person who had murdered the three people inside did not have any key on him.

No one inside the driver's cart would willingly let anyone in who is not part of the train staff. They would also not leave it unlocked accidentally to avoid someone breaking in.

The drivers did not open the door for anyone.

Neither of the drivers left the driver's cart during the story.

The culprit never opened any roof panel.

Killing people:

Spoiler for Hidden:

There were no accidental deaths.

At least 1 death occurred in the driver's cart while the door was completely closed.

Marcia was already inside the Driver's cart when the first murder occurred.

Marcia was in the same room as the culprit when she was killed.

The murderer was not even inside the driver's cart when the first murder occurred inside there.

The culprit did not throw anything into the room when the door/roof panel was open.

None of the deaths in the Driver's Cart were a result of any explosion.

Marcia did not bring anything into the cart.
This includes being forced to wear and deliver something on her to the Driver's cart.

Not all deaths inside the driver's cart were killed the same way.

Miscellaneous:

Spoiler for Hidden:

Every conductor on the train always had possession of their key while alive.

The only way for an object (except light, lightning, heat or sound) to enter the driver's cart is through the roof panel or through the main door between the 2nd  and 1st cart.

The weapon used to kill the three people inside is not something you would find 'conventional' (i.e. - not a firearm or a meelee object that was designed to be a weapon).

No one was killed from shockwaves or high temperatures.

If someone tried to electrocute people through a metal wall, the attack would affect everyone on the train (regardless of position) equally.

None of the people you saw in the driver's cart brought anything inside the cart that was considered poisonous. Also, none of the surfaces of the driver's cart was poisoned.

If any harmful gas was detected in the driver's cart, any of the people inside would have been alerted and would simply open the roof panel and/or driver's door to ventilate/escape the room (and temporarily allow the train to autopilot).

[UTAlan]

Marcia was already inside the Driver's cart when the first murder occurred.

Marcia was in the same room as the culprit when she was killed.

The murderer was not even inside the driver's cart when the first murder occurred inside there.

Wait, what? Is this not a logical error?

[UTAlan]

Oh, nevermind. That just requires the murderer to have entered the driver's cart, or Marcia to have left it, after the first murder and before her murder.

[Submachine]

Marcia and the drivers were inside the Driver's cart when the first murder occurred. One of the drivers were killed from the distance, either through an opening (door, roof panel, other holes), through the wall or by a prepared/timed effect inside the Driver's cart.

We also know that Marcia didn't left the Driver's cart, so the culprit had to step in the cart, either through the door or the roof panel. When he was in, he just had to kill Marcia and the other driver with non-conventional weapons/methods.

[Fippe94]

The murderer placed explosives on the roof panel/roof/window. The explosion broke the panel and the window, killed at least one of the drivers, and made the door swing open. Then the murderer entered the cart and killed the remaining person(s).

[Kuroaitou]

The murderer placed explosives on the roof panel/roof/window. The explosion broke the panel and the window, killed at least one of the drivers, and made the door swing open. Then the murderer entered the cart and killed the remaining person(s).

There were no explosives placed on the outside of the train.

[Submachine]

The culprit activated a remote control, which caused the driver's counter to have a short circuit and explode. A driver or 2 died in the explosion. Marcia, who was inside the room, opened the door in panick, but the culprit was waiting outside. He then pushed Marcia back on the floor, closed the door behind himself and suffocated her with a VELCRO DETACHABLE PILLOW.

[Fippe94]

The murderer placed explosives right outside the room, on the inner wall of the train or on the door itself. The explosion broke the panel and the window, killed at least one of the drivers, and made the door swing open. Then the murderer entered the cart and killed the remaining person(s).

[Kuroaitou]

The culprit activated a remote control, which caused the driver's counter to have a short circuit and explode. A driver or 2 died in the explosion. Marcia, who was inside the room, opened the door in panick, but the culprit was waiting outside. He then pushed Marcia back on the floor, closed the door behind himself and suffocated her with a VELCRO DETACHABLE PILLOW.

The murderer placed explosives right outside the room, on the inner wall of the train or on the door itself. The explosion broke the panel and the window, killed at least one of the drivers, and made the door swing open. Then the murderer entered the cart and killed the remaining person(s).

Tag-teaming me, eh?
The culprit had no way of short circuiting the driver's counter/dashboard/train controls.

If an explosive was placed right outside the room or on the door of the driver's cart, the explosion would have also caused damage to the 2nd cart (windows, walls, etc.). There was no such damage in the 2nd cart.

[UTAlan]

Do we think this might provide any clues? Maybe not, but I am looking for anything we might be missing.

You eavesdrop on the conversation that Patty and Marcia were having, despite their 'whispering'...

"I don't know about Jack's behavior, but he won't do it again I think... it'll all be okay, right Marcia?"
"It won't be if I catch him pulling the same ******* **** one more time. Tired of him getting away with his laptop abu-"