Book ending spoiler alerts!!
In the Maze Runner book, Gally runs into the maze after a Gathering is held between all of the Keepers.
Gally later goes missing until the end of the book when the Gladers get out of the maze. Ava, the scientist reveals there is one more Variable. Gally mentions "They... can... control me". Then he throws a knife killing Chuck under the control of the Creators.
When Gally snapped in the Gathering, was he pissed off, or was he under control of the creators the whole time?