Law & Order: Special Victims Unit Episode 6.06 Conscience

The son of psychiatrist Dr. Brett Morton (played by Kyle McLachlan) disappears from a birthday party, and is found dead by his friend. Despite viewing his child's body in the morgue, Morton remains perfectly calm and asks carefully-laid questions to Stabler, which fills the Detective with unease. When it becomes clear that the little boy who found the body of Morton's son is actually the killer, the police question children who knew both of the boys. Testimonies bring to light that the boy is a sociopath with violent tendencies. Dr. Morton loses his composure in court when this is brought to light, snatching an officer's gun and shooting the boy dead. As a claim of defense during his subsequent trial, the Doctor claims he was not aware of what he doing, and his despair overrode his senses. He rationalizes that the killing was just, because the unrepentant boy would have just gone on to kill again, but he wouldn't.