My wife was attacked by a burglar when I was on my way home from work. She stabbed him with a butcher knife and killed him. The police say it was an obvious case of self-defense. When I went to pick her up from the police station, she said. - "When I heard the doorbell I thought it was you, but then a masked man jumped me as soon as I opened the door!" - "You must have been so scared" - I said - "But you're safe now" - I hugged her tightly. How did she kill the burglar so fast when he attacked her at the door?