The Witch's Game 4

[Kuroaitou]

Fine.

The murderer entered the driver's cart when Marcia had opened the door to it. Once he had entered he closed the door behind him. Then he killed the three in there and left.

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

Same truth, minor modification.

The culprit bumped into Marcia on the way to the Driver's cart and pointed a gun at her. An explosive belt was attached to her, she was then forced to open the door to the driver's cart with her Conductor's Key. The culprit then pushed Marcia in the room, then quickly closed the door. The blast killed everyone inside, cracked the windshield and bursted the roof panel open.

Marcia did not wear any explosive on her before entering the driver's cart.

[Fippe94]

The murderer got gas into the driver's cart, through the ventilation system or under the door, which forced the people inside to open the roof panel. When they had done this, the murderer was on the roof and threw down a grenade os similar explosive and killed them.

[Kuroaitou]

The murderer got gas into the driver's cart, through the ventilation system or under the door, which forced the people inside to open the roof panel. When they had done this, the murderer was on the roof and threw down a grenade os similar explosive and killed them.

Black truth extended:
The culprit did not throw anything into the room when the door was open. --->

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

[Fippe94]

Repeat this: The only ways for objcts to enter the driver's cart is through the roof panel and through the door.

[CrockettRocket]

Spoiler for silly post, havnt fully read the OP, may not make sense:

The murderer got gas into the driver's cart, through the ventilation system or under the door, which make the people on the inside go berserk and break a hole in the wall. When they had done this, the murderer had thrown a grenade or similar explosive through the opening.

[Kuroaitou]

Repeat this: The only ways for objects to enter the driver's cart is through the roof panel and through the door.

Extensive repeat:
The only way for an object (as in a material/physical object, not energy such as light) to enter the driver's cart is through the roof panel or through the main door between the 2nd  and 1st cart.

Stated this just in case someone brings up lasers or some other ridiculousness into this...

Also CR - bold it for me please? ^^ NEVERMIND:

The murderer got gas into the driver's cart, through the ventilation system or under the door, which make the people on the inside go berserk and break a hole in the wall. When they had done this, the murderer had thrown a grenade or similar explosive through the opening.

The train walls cannot be broken open.

[CrockettRocket]

Fixed

[Submachine]

Sorted things out a bit.

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.

The culprit never opened any roof panel.

Killing people:

Spoiler for Hidden:

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.

The murderer did not place any explosive inside the room.

No one entered the driver's cart with any explosive device (hidden or otherwise).

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

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).

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).

[Fippe94]

The murderer entered the room when Marcia openend the door, put a bomb inside the room, then quickly exited the room, and closed the door.

[Kuroaitou]

The murderer entered the room when Marcia openend the door, put a bomb inside the room, then quickly exited the room, and closed the door.

The murderer did not place any explosive inside the room.

[CrockettRocket]

Repeat: The murderer entered the room when marcia opened the door, then exited the room and closed the door.

[Submachine]

The culprit knew how to electrocute everyone in the Driver's cart from the outside, but you could say that it was an inside job. Get it? He then forced Marcia to open the door and go in. After she was inside, she was killed by a non-conventional weapon and the culprit left the scene.

Spoiler for failed truth:

The culprit suffocated Marcia with a Velcro detachable pillow outside the Driver's cart, then took her keys. He used the key to enter the door, then closed it right behind him. He then used a non-conventional weapon to kill the 2 drivers inside, and after they were dead, the culprit opened the door, dragged Marcia's dead body in and then left the scene.

The Velcro detachable pillows were placed back afterwards.