Harlan tries to fire at Grady but, because the gun is empty, he only gets 3 clicks as he pulls the trigger. However, the slide should have locked open when he fired the last shot and even if it had closed, the striker-fired pistol he is holding would only click one time no matter how many times he pulled the trigger. The striker is released the first time the trigger is pulled and will not click again without the slide being racked open again.