Logan is widely considered to be the best X-Men film from the 20th Century Fox franchise. Set in 2049, where the mutant population is decimated, the once headmaster of Xavier's School for Gifted Youngsters, Charles Xavier, suffers from a degenerative brain disease. Now that the X-Men are dead and disbanded due to the mysterious Westchester incident that he inadvertently caused, it is indeed the end of an era. Still, the tragedy that unfolded inside the X-Mansion is never fully explored on screen.
While the audience was left to fill in the blanks and try to piece together the event using context clues, it's not hard to imagine what horrors specifically occurred, especially since the scenes set at the Oklahoma casino hotel showcased the dangers of an Omega Level Mutant's unstable mind when their telepathic powers are uncontrollably unleashed. Still, many fans were disappointed to learn that a flashback scene graphically depicting the Westchester incident and the death of the X-Men was cut from the script before it could be filmed; although, there are hints about what happened.
During the Oklahoma casino scene, Xavier has a seizure, sending his mutant powers spinning out of control. Xavier unintentionally causes everyone in the area to experience an extraordinary amount of pain as they remain paralyzed in place. The only way Logan and Laura can stop him from killing all life in the vicinity is to forcibly inject him with medication, which is no small feat. Later, a broadcast over the radio reveals that both the casino event and the Westchester incident are strikingly similar, giving the audience insight into what Xavier is capable of when he no longer has a handle on his deteriorating mind.
Although the tragic event reportedly injured six hundred people and took many, if not most, of the X-Men's lives, much of the details surrounding the Westchester incident have intentionally been kept under wraps. What fans know is that Xavier released a deadly psionic wave due to a seizure, so now his mind is classified as a Weapon of Mass Destruction. Since this catastrophe compares directly to the casino situation, it is safe to assume that the circumstances are identical to the tragedy that hit Xavier's School for Gifted Youngsters. While it would've been memorable to see this play out, there were reasons behind leaving the death of the X-Men off screen.
"There are versions we wrote that were never filmed with the actual flashback of what happened," director James Mangold explained to The Hollywood Reporter, "but I've found the experience of watching it is far more poignant to just know that it was something really regrettable and it was bad and most likely, friends were lost. Or maybe it was people we didn't know." Be that as it may, some of fans disagree with this decision to ax the scene, as this could've given more closure to the X-Men; however, it could've also stolen the show, as Mangold, according to that same interview, "wanted to make a movie less about information and more about character."
Logan is already gruesome and sorrowful enough as it is, so to incorporate shots of the X-Men dying most likely would have detracted from the nuance of the story. After all, portraying a mass murder where Xavier kills his protégés would have some hard-to-forget imagery considering fans spent nearly two decades getting to know these characters. Perhaps it is for the best that the massacre was omitted because it could have overshadowed the rest of the film or made Xavier less sympathetic to the audience.