At least 30 armed men invaded a drug-treatment center in northern Mexico late Thursday night, killed 19 patients and wounded four others, the state-run Notimex news agency reported Friday. Witnesses told authorities the armed men marched 23 people outside, lined them up and shot them, Notimex said, citing Director of Police Intelligence Saul Hernandez. The wounded were taken to hospitals under heavy guard, the news agency said. Shootings at drug-treatment centers have become more common as Mexico's drug cartels and street gangs ramp up their violence An attack at the El Aviane rehab facility in Ciudad Juarez in September left...