LOS ANGELES — The nation’s two largest school systems confronted threats of a terrorist attack on Tuesday and reacted in sharply different ways: New York City reviewed the warning and dismissed it as a hoax, but officials here abruptly shut down all public schools, upending the lives of parents, students and teachers.
The emailed threats to school officials on both coasts — which spoke of teams of jihadists using guns, bombs and nerve gas to attack public schools — were largely identical in their wording, and both had been routed through a server in Frankfurt, apparently by the same person, officials said.
The Los Angeles schools chancellor, Ramon C. Cortines, reviewed the threat, which came in to several school board members around 10 p.m. on Monday, with police officials here early Tuesday before deciding to send out an alert closing nearly 1,100 schools and asking parents to keep the district’s 640,000 children home. “I as superintendent am not going to take a chance with the life of a student,” he said at a 7 a.m. news conference.
In New York, the police commissioner, William J. Bratton, reviewed the New York version of the threat and decided it was “a hoax.” Later on Tuesday, officials said that they believed that the email in Los Angeles was also most likely a hoax and that schools will reopen Wednesday.
“We can now announce the F.B.I. has concluded this is not a credible threat,” said Mayor Eric M. Garcetti of Los Angeles. “It will be safe for our children to return to schools tomorrow.”
The contrasting responses, and the not-so-subtle cross-country backbiting that marked the day — Mr. Bratton said Los Angeles had overreacted, and officials here defiantly said they had not — was to some extent a reflection of the long and subtle competition between these two coastal cities, whose leaders have sometimes shuttled back and forth. Mr. Bratton once served as police chief in Los Angeles, and Mr. Cortines once ran the schools in New York. Both cities have grappled with major terror attacks and threats.
“We’ve come to the conclusion that we must continue to keep our school system open,” said Bill de Blasio, New York’s mayor. “In fact, it’s important — very important not to overreact in situations like this.”
But the reaction in Los Angeles was as much an insight into the tense times that have gripped this region since Dec. 2, when an attack 50 miles from here left 14 people dead and 22 injured. Southern California has been on edge much the way the New York region was after the terrorist attacks of Sept. 11, 2001.
Officials here said that they were prepared for second-guessing but that given the fresh memory of the San Bernardino massacre — and that investigators were exploring whether the husband and wife attackers might have also been targeting schools — Mr. Cortines had made the prudent call.
“It is very easy in hindsight to criticize a decision based on results that the deciders could have never known,” said Charlie Beck, the chief of the Los Angeles Police Department, who is close to Mr. Bratton. “All of us make tough choices. All of us have the same goal in mind: We want to keep our kids safe.”
“These are tough times,” he said. “Southern California has been through a lot in recent weeks.”
Josh Earnest, the White House press secretary, said in a briefing that the administration would not “second-guess the decisions that are made by local law enforcement officials in any community across the country” in responding to terror threats.
Officials in New York said they were not aware of the email that had been sent to Los Angeles when they made their decision. Similarly, Mr. Garcetti said officials in Los Angeles were not aware of the threat to New York when they made their choice.
The decision here threw the lives of millions of people — students, parents, teachers — into disarray and sent a wave of concern across an already tense region. “If they sent an alert, I never received it,” said Christine Clarke, who showed up at Hollywood High School looking frantically for her son after hearing the news on the radio. Parents scrambled for last-minute day care or called in sick at work, while students suddenly found themselves with a day off — during final exams week, no less.
“When are finals going to be now?” John Guanzon, 16, a junior, asked a school guard as he arrived, books in hand, at Hollywood High.
Representative Brad Sherman, a Democrat who represents parts of Los Angeles, said in an interview that the writer of the threat claimed “he has 32 jihadist friends” ready to attack the schools using bombs, nerve gas and rifles. The writer identified himself as an observant Muslim who had been bullied while attending a Los Angeles high school, according to Mr. Sherman, who said he had been given a copy of the email by a school board member who had received it.
Mr. Sherman said elements of the message did not appear credible, including the number of potential attackers and the claim that they had access to nerve gas. (Mr. Bratton, in New York, suggested that the writer might have been inspired by recent episodes of “Homeland,” with its plotline of a sarin gas attack on Berlin.) The message was signed by a male Arabic-appearing name, Mr. Sherman said, but added: “The word ‘Allah’ appears several times in the email, but once it’s not capitalized. A devout Muslim or an extremist Muslim would probably be more careful about typing the word Allah.”
The author appeared knowledgeable about the structure of the Los Angeles Unified School District, referring to the system by its full name, which added to the concern, Mr. Sherman said. “Just because parts of the email are false doesn’t mean it’s all false,” he said.
The threat to New York schools was sent to an Education Department official around the same time as the one to Los Angeles but was not seen until around 5 a.m. Tuesday, said a law enforcement official who spoke on the condition of anonymity because the official was not authorized to discuss details of threat publicly. The official said the writer in this case said he had 138 jihadist friends who would abet him.
Stephen Davis, the New York Police Department’s top spokesman, said the emails threatening the two cities “were the exact same wording with the exception of putting in the cities’ names and changing the number of people who were supposed to be participating in it.”
Across the country, Mr. Cortines said he saw no choice but to close the schools. “It was not to one school, two schools or three schools — it was many schools, not specifically identified,” he said of the threat.
Mr. Cortines initially said schools would remain closed until the police and school administrators had searched every building. The logistical task was immense: The Los Angeles district has more than 640,000 students enrolled in 900 schools and 187 public charter schools across more than 720 square miles. In the end, officials said, they cut the search short after 1,531 school sites had been inspected as of Tuesday evening.
While some people around the country criticized Los Angeles for setting a precedent — showing that pranksters, or worse, could hobble a major city — many Angelenos said they sided with the city.
“We’re part of the impact zone of San Bernardino, so the ripple effect can be felt,” said Rudy Perez, the first vice president of the Los Angeles School Police Association. “So it’s better to be cautious.”