DUNCAN, Okla. (AP) — Authorities in southwest Oklahoma have arrested a teenager on suspicion of threatening a shooting at a high school. Duncan police say the threat was posted on the social media application Yik Yak. Lawton television station KSWO reports (http://bit.ly/1wIUXVj ) that a 15-year-old boy was arrested late Wednesday in connection with the postings. The station reports that the postings threatened a shooting Thursday at Duncan High School. School officials say there will be extra security on campus Thursday as a precaution. ___ Information from: KSWO-TV, http://www.kswo.com