Police say they were shooting down criminals who had been on an army patrol . They said some criminals had fled to Technological Institute of Higher Education of Monterrey . Initially , officials said mechanical engineering graduate students were drug gang members . The school 's rector blamed himself for the mix-up in identities . Interior Ministry apologizes for deaths , promising more intense investigation .
Police say they were shooting down criminals who had been on an army patrol . They said some criminals had fled to Technological Institute of Higher Education of Monterrey . Initially , officials said mechanical engineering graduate students were drug gang members . Interior Ministry apologizes for deaths , promising more intense investigation .