In the marketing of “Trap,” the twist that Cooper is actually the serial killer was given away implying it’s case closed, pencils down, and everybody can go home.
Not being content with that, Shyamalan has Cooper kidnap the star of the concert and disguise himself as SWAT to escape another hairy close call with being caught.
Returning to his home, Cooper admits to his wife the rage bubbling inside him. Only a hallucination of his mother unbalances him enough for the cops to arrive and arrest him.
Pausing to adjust his daughter's bike, he's ushered into a SWAT van. We see Cooper's face one last time having broken off a small piece of bike to free himself of his handcuffs.