Uncle John Cooke is a minor antagonist in the 2016 psychological thriller Split.
He was portrayed by NFL football player turned actor Brad William Henke.
In the film, John only appears in flashbacks from over ten years before the events of the film. He is the younger brother of Mr. Cooke, and by proxy the paternal uncle of the film's protagonist Casey Cooke. He also mentions that his and Mr. Cooke's father (Casey's grandfather) died of a heart attack which runs in the family. John is a skilled deer hunter, but however, he is also a sadistic pedophile who enjoys molesting young children, primarily Casey, yet it's unknown if she's the only child he has molested in the past.
In the flashbacks, Mr. Cooke was a single father to five year old Casey, and the two, along with Uncle John, would go on hunting trips in the rural Pennsylvania backwoods. Uncle John at first was a likable supporting character who told stories to Mr. Cooke and Casey while they dined in a local restaurant during their hunting trips, as well as being knowledgeable in hunting. However, his nature was revealed when he lured his niece Casey into the woods as Mr. Cooke slept one morning, and he was on all fours naked wanting to "act like animals" with her, telling her to take off her clothes or else he would tell her father she was misbehaving. After he had finished molesting her, not shown in the film, John was getting dressed and returning to the site when Casey pointed a shotgun at him for what he had done. Casey was too scared and John pulled the gun away from her.
Sometime later, Mr. Cooke died of a heart attack the same way as his and John's own father, and John became Casey's legal guardian, allowing him to continue molesting her well into her teen years. Although it can be presumed that Casey cut herself because of the abuse, one can presume that John did some of the mutilation to her as well.
John (off screen) was to pick up Casey, now a teenager, from a birthday party at King of Prussia Mall in suburban Philadelphia, but she, along with Claire Benoit and Marcia, were kidnapped by "Dennis" (a personality of Kevin Wendell Crumb). Days later, John (again off screen) arrived at the Philadelphia Zoo where Casey was found, and when Casey was informed, it was implied that she would report John to the police.
Until the 2019 release of Glass, it was revealed that John was indeed arrested.