Gunmen killed two police officers and six other people in less than 48 hours, the latest victims in a wave of drug-related violence in northern Mexico, police said Friday. Investigators say the Sinaloa Cartel is fighting the Gulf Cartel for billion-dollar drug smuggling routes into the United States. The battle has led to beheadings, grenade attacks and execution-style killings across Mexico and the violence has taken a particularly heavy toll on police. The latest killings were in the northern Mexican metropolis of Monterrey in Nuevo Leon state, a hot spot for violence where 42 people have been killed since Jan. 1. Full Story