It is not a typo. What it means is that his personality led him to confront an intruder, where someone with a different personality might have investigated further, or gone for help, or made some other choice. It means his nature, and he's saying that for him to have made other choices in that situation would have required that he be a different type of person. It's his excuse for why he did what he did, not a way to claim or deny responsibility.
Full Transcript is at http://news.sky.com/story/1240765/oscar-pistorius-trial-court-transcript. Page 10, Pistorius is quoted saying he acted in his nature, and it fits the context of the article you cited.