searching hundreds of public schools after officials say they received an e-mail threat this morning. the school superintendent in los angeles shut down the entire district at the height of the morning rush. l.a., keep in mind, is the country s second largest school district. more than 600,000 students were forced to stay home. at the same time the nation s largest school system, new york city, also working its own e-mail threat today but officials in the city there say that was a hoax. los angeles police chief charlie beck said that when authorities began investigating, they discovered a number of issues that prompted the shutdown. here he was. the e-mail was very specific to l.a. you know nied school district campuses and it included all of them. it was also very specific about the threat, the implied threat.