Tracked Down & Killed

While much of the film focuses on Wolverine, Charles Xavier, and X-23, there is a small, redemptive story arc for another mutant: Caliban. When we first meet the albino mutant — played by Stephen Merchant — he's helping Wolverine look after the frail and wheelchair-bound Charles, who is suffering from Alzheimer's and is prone to seizures.

Later on in the film, we learn that Caliban used to work for Alkali Transigen, using his mutant abilities to assist the sinister and powerful corporation with tracking down any mutant stragglers that had managed to survive in this dystopian near-future. Once caught, they were experimented on and killed. At some point along the way, Caliban had a change of heart, left Transigen, and ended up as one of Charles's caretakers.

So, yes, Caliban is responsible for the death of a good number of mutants, but what he did pales in comparison to the other reasons that will be provided in the following slides.

The Westchester Incident

Logan is loosely-based on the "Old Man Logan" storyline from artist Steve McNiven and writer Mark Millar that ran from 2008-2009. Like the film, "Old Man Logan" was also set in a violent, dystopian future, but instead of all mutants being nearly extinct, supervillains banded together to destroy superheroes and rule the world. One of their crowning and most evil achievements, which is shown via a flashback sequence, came when Mysterio tricked Wolverine into killing his X-Men teammates — who he thought were a gang of supervillains invading the X-Mansion. After that heart wrenching and stomach churning incident, Logan renounced his Wolverine persona and lived a quiet life on a farm with his wife and two children in the western United States.

In the film, we learn that Charles's mental and physical health has been rapidly degrading over the years due to old age and Alzheimer's, and because of that, he is prone to seizures. When those occur, he can't control his telepathic mutant abilities, so he unknowingly unleashes powerful psychic blasts that put nearly everyone around him in a extremely painful and potentially lethal paralyzed state.

Though it is never shown, we find out in bits and pieces via a conversation Donald Pierce (Holbrook) has with Logan, a radio news report, and in Charles's last moment of clarity that the professor suffered a seizure that led him to accidentally paralyzing 600 people and killing the remaining X-Men (except for Wolverine) during "The Westchester Incident."

"I don't deserve it, do I?" Charles says after enjoying a restful night of sleep at an Oklahoma farm (via VF). "I did something. . . something unspeakable. I remembered what happened in Westchester. This is not the first time that I've hurt people. Until today, I didn't know. You didn't tell me, so we kept on running away from it. I think . . . I finally understand you."