A forensic technician ties a used police line together to seal off a crime scene in Monterrey Feb 8, 2012.A taxi driver was shot dead by gunmen almost at the same time when another group of hitmen attacked three taxi drivers in a different neighborhood, killing two and injuring one, according to local media.[Photo/Agencies]

Police officers from the State Attorney General's Office stand together in a hall before escorting suspects to a presentation to the media, in Monterrey Feb 9, 2012. [Photo/Agencies]