Authorities say a 15-year-old sophomore opened fire at his Michigan high school, killing three other students and wounding six other people, including a teacher. Oakland County Undersheriff Mike McCabe said at a news conference that he didn't know what the assailant's motives were for the attack Tuesday afternoon at Oxford High School in Oxford Township, a community of about 22,000 people roughly 30 miles (48 kilometers) north of Detroit. Authorities arrested the suspect at the school and recovered a handgun.