The threats arrived at the same time on opposite sides of the country.
Shortly after 10 Monday night — about 1 a.m. on the East Coast — public school officials in Los Angeles and New York received nearly identical emails promising imminent attacks on campuses involving explosives and gunmen.
The immediate response in both cities was the same: Call the police and the FBI.
There, however, the parallels ended.
An hour before the sun rose in Los Angeles, the head of the sprawling school district made the dramatic decision to close the district's more than 900 schools for the day, upending the routines for 640,000 students and setting off a massive response as police began to scour campuses.
Police in New York, meanwhile, concluded the threat was bogus — the unconvincing work of an impostor.
Cross-country sniping followed quickly.
The move in Los Angeles was "a significant overreaction," New York Police Commissioner William J. Bratton, who once ran the LAPD, said bluntly.
"We cannot allow ourselves to raise levels of fear," Bratton said to reporters. "This is not a credible threat and not one that requires any action."
His boss, Mayor Bill de Blasio, said the email threat was "so generic, so outlandish" that it couldn't be taken seriously.
"It's very easy to second-guess decision-makers when you don't have to live with the consequences of the decision," Los Angeles Police Chief Charlie Beck, a disciple of Bratton's, fired back. "These decisions are not something you get to do over again if you turn out to be wrong."
Later in the day, he conceded that the threat was not credible. But in the early morning, nothing was clear.
The email, Beck said, was sent to members of the L.A. Unified Board of Education, which oversees a massive district spread over more than 720 square miles.
Los Angeles school board President Steve Zimmer opened his email Monday night, saw the threat and immediately notified the district's police chief, who in turn contacted the LAPD. The LAPD alerted the FBI.
About 3 a.m., Beck was alerted to the email. He was told that investigators had traced the message to an Internet server in Germany, but was cautioned that it might have been rerouted from somewhere else.
Shortly before Beck learned of the unfolding crisis, a high-ranking official in the New York City school system was starting the day with a check of emails that had arrived overnight. Seeing the ominous message, the official set in motion an investigation like the one already underway in Los Angeles.
In Los Angeles, Beck said he was troubled by the "very broad ... but also very specific" nature of the threat.
The email, he said, listed the name of every L.A. Unified school and suggested that high schools were the primary target. The sender wrote that the attack would occur Tuesday and warned that explosives had already been planted. After they detonated, people "with ISIS connections" would attack with AK-47 rifles and other guns, said Beck, who was paraphrasing the email.
"It was also in very good English — which is not a good sign," he said. "Most of the hoaxes that I see … have syntax errors, a lot of incomplete sentences, non-sequiturs. So that concerned me."
It was not until 5 a.m. that Supt. Ramon C. Cortines learned of the situation. Cortines, who announced his retirement months ago, had already begun to transition out of the job and his second in command, along with the school police chief and other top district officials, worked throughout the night without alerting him.
Shortly after he was told, Cortines made the decision to close schools.
Beck said the move showed great courage.
"We gave them our best counsel, we gave them the best investigative information we had," he said, declining to say what recommendations police gave school officials about closing campuses.
The first notice of the closures went out to district administrators at 6:25 a.m. An email went out to parents five minutes later.
The scene in New York was far different.
The threat sent to New York claimed that schools would be attacked with a combination of pressure cooker bombs, nerve gas agents and machine guns, according to a law enforcement source who read the email but was not authorized to release details. The sender said "138 comrades" would help carry out the attacks and that students at every school would be massacred.
Stephen Davis, deputy commissioner of the New York Police Department, said investigators were struck by small but significant errors in the email's wording.
The message, for example, claimed that the attacks would be carried out in the name of Allah, but the sender used a lower case "a." The email also included a large amount of information about the threatened attacks, which runs counter to common practices of terrorists, Davis said.
"It didn't add up," Davis said. New York police, like those in Los Angeles, declined to release copies of the emails, citing their ongoing criminal investigations.
Not long after they began digging into the email, New York officials learned of the threat received in Los Angeles. That made it easier for them to conclude the emails were fakes, because the wording was nearly identical and the sender was claiming to be in both cities at the same time.
Between 8:30 a.m. and 9 a.m. in New York, officials formally decided that the threats were unbelievable.
Los Angeles police didn't learn of the New York threat until hours after the decision to close the Los Angeles schools was made.
"By that time, the horse was out of the barn," Beck said.
The chief said he understood how the recent attacks in San Bernardino could have influenced the school district's decision. "The tension in L.A. is palpable right now," he said. "People are very concerned."
"Would you send your kid to school?" he asked. "Even if it's just a small possibility, why would I?"
Times staff writers Howard Blume and Richard A. Serrano contributed to this report.
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