UPDATE, 3:00pm ET: Trace Gallagher reported the latest details moments ago, saying that for all intents and purposes the emails sent to New York City and Los Angeles schools were the same. 

Some red flags, according to officials, were that the so-called Muslim extremist did not capitalize "Allah," made a pornographic reference and made highly unrealistic claims.

The email reportedly threatened a massacre of schoolchildren with pressure-cooker bombs and guns.

Gallagher said that the Los Angeles school superintendent was the final decision-maker on keeping 640,000 students home and that the FBI did not recommend the closure. 

The school district police force is now sweeping its more than 1,000 campuses.

Rep. Brad Sherman (D-CA) told Shepard Smith that the email sent to L.A. schools was more specific than the one sent to New York City. 

Sherman said the writer of the Los Angeles email claimed to have 32 "jihadist accomplices."

UPDATE, 1:20pm ET: Officials in Los Angeles are taking some heat for closing schools. The FBI and NYPD deemed the same threat to be not credible. 

The police chief responded by saying that it's "easy to criticize a decision when you have no responsibility for the outcome of that decision." The mayor defended the closure by saying the city acted out of "an abundance of caution."

New York City Police Commissioner Bill Bratton said he believed Los Angeles authorities overreacted significantly.

Bratton said the NYPD reviewed the same email threat, and judged it to be a hoax.

"In reviewing it, the instigator of the threat may be a 'Homeland' fan," he said, referring to the popular Showtime series that showcases the CIA.

"Basically, watching 'Homeland' episodes, it mirrors recent episodes on 'Homeland,'" said Bratton.

All of Los Angeles' public schools have been closed today due to an electronic message described by officials as a "credible threat."

During a press conference, L.A. Unified School District Police Chief Steven Zipperman said the threat was still being evaluated.

District Superintendent Ramon Cortines would not detail the threat but described it generally as a "message."

Schools would remain closed until the threat was cleared, which officials said could happen by the end of the day.

It's the country's second largest school district, serving 640,000 students.

The L.A. School Police Twitter account instructs parents and guardians to bring proper ID when picking up their child at school.

Follow @LASchoolPolice on Twitter for check FoxNews.com for the latest updates.