Right before the accident you will enter a room with two scientists. They will talk to each other. After they are done and have opened the door, make one of the scientists stand on where the door should be. Once you go into the room, the door should shut behind you, with the scientist trapped in between it. Once you have put the rock into the laser, run into the room with the two scientists and hide out of sight from the laser. This should make the sequence to Zen not happen. When the next chapter begins, the scientist you trapped in the door should still be there.