Law & Order: Special Victims Unit 7x12

Monica Phelps is found dead in her apartment, her son Nathan hiding in the closet behind her body. Detectives soon link Monica's death to philanthropist Ted Carthage, who runs an organization dedicated to helping people get off the streets. Benson is certain that Carthage is the killer, but a shaky ID from Nathan puts him back on the street. After Nathan kills Carthage himself, Sophie Devere argues that Nathan committed the killing because he saw Carthage shoot his mother -- something the gun manufacturers don't like.