More regarding School closures in Los angeles

It was said on CNN that the emails that were sent to all school board officials of LAUSD contained the following information:
1. 32 people as well as the emailer would be involved
2. Assault rifles and bombs would be used
3. This was enough similarity to San Bernadino that they didn't want to take any chances.

Because:

What was known about the 2 assailants in San Bernadino before the shooting and attempted bombing there?
Nothing.

In fact the lady was still on a green card one can get for an intended spouse from another country. So, when she came into the country she wasn't a citizen or a green card holder yet and still was on a green card  for an intended wife of a U.S. citizen.

So, because this was very different than other less sophisticated bomb threats they get every day, and because of the 14 dead and 21 injured from San Bernadino the school superintendent closed the schools and was then supported by all the law enforcement in Los Angeles County and Federal Law Enforcement as well.