Local, state and federal officials converged on campus Wednesday after Director of Public Safety Ed Callahan received an anonymous e-mail threatening a "planned terrorist attack" on campus. Callahan received the threat against the Heller School for Social Policy and Management about 11:30 a.m., prompting an evacuation of the graduate school and, as an added precaution, the science complex.

"As far as I'm concerned, this was a major atrocity," Callahan said, referring to the threat.

Callahan declined to release a copy of the e-mail or the sender's address, saying the investigation is still ongoing.

The Justice received an anonymous tip, which was confirmed by Detective Bussy Adam of the Newton Police Department, that the threat originated from a computer at the Newton Free Library.

Kathy Glick-Weil, the director of the library, said she did not see any suspicious people Wednesday, and that she was unsure how authorities managed to trace the e-mail.

"I just don't know how they did it, and they certainly weren't telling us how they did it," she said, adding there was a significant police presence around the library.

The University also shut down operations at about 4:45 p.m., advising people to remain indoors until authorities completed searching the buildings in question, which occurred about 6:30 p.m.

Callahan said the Waltham police and fire departments, state police, and the FBI were among the agencies called to campus. In total, 40 to 50 officials and bomb-sniffing dogs investigated the threat, he said.

"For this type of scenario, this is consistent to what we were dealing with," Callahan said, adding that if the situation had presented itself, he could have called in more authorities.

Although six bomb threats have been made on the University since 2003, including three in a span of two weeks that year, Callahan said he believes this is the first threat alleging a planned terrorist attack against the University.

After reading the e-mail, Callahan contacted Library Technology Services to pinpoint its origin. He then contacted outside law enforcement agencies to help conduct the investigation.

Heeding advice from authorities, the University began evacuating the Heller School at about noon. Callahan led the evacuation, which took 45 minutes-not long, considering the inclement weather and the number of people inside, he said.

"From the law enforcement perspective, we acted expeditiously," Callahan said.

The science buildings, though not mentioned in the e-mail, were evacuated at 1:30 p.m. Law enforcement officials worried that chemicals inside the buildings could inflict significant harm in the event of a terrorist attack, Callahan said.

Active science experiments caused the evacuation to last more than one hour, Callahan said.

"It's a larger complex that required more resources to evacuate," Callahan said. "At one point, I had 15 teams of two that split up and went through that building."

John Pearlson '08 was in a biology laboratory trying to breed a type of fruit fly when his professor told everyone to leave. Pearlson said the entire class, about 40 people, will have to redo the lab with the other section, making it more difficult to complete.

"The entire section was outraged by the situation," Pearlson said.

In a press conference Wednesday afternoon, Waltham Police Chief Edward Drew said authorities were conducting thorough examinations of the Heller School and science complex.

"We activated a safe, sound plan to facilitate the least amount of destruction and damage if there was ever any kind of hazardous condition that took place," he said.

Drew also said about 250 residents who live near campus were notified of the "hazardous materials condition" via the city's reverse 911 system. The message warned residents to remain inside and lock their windows and doors until further notice.

Chief Operating Officer Peter French followed suit by sending an e-mail about 5:30 p.m., asking that everybody remain indoors. It would be another hour and a half before this suggestion was reversed.

As an added precaution, Waltham police also evacuated the Stanley Elementary School on South Street. Drew said the school was closed in case the road needed to be shut down.

"We didn't want parents concerned about picking up their kids," he said.

Waltham Mayor Jeannette McCarthy was at the school when it was evacuated.

"I think, all things considered, everything went well, and I want to thank everybody for getting the kids out expeditiously," McCarthy said.

In one of the six bomb threats since 2003, a student was arrested last May for allegedly e-mailing a bomb threat to several administrators, resulting in the shutdown of the Sachar Academic Complex and final examinations occurring in that building.

The student returned to Brandeis last semester after the case against him was thrown out because the prosecution could not produce key witnesses at trial.

French said that it is too early to tell if the person who sent the threat will be caught, but that he certainly hopes somebody is convicted "because this has created a lot of anxiety and disruption on campus."

Drew said his department is working closely with the FBI, and that new information will likely become available later this month. He also said the threat is a federal crime with a maximum sentence of 20 years imprisonment.

"The total disruption that threat caused is something that deserves more than a fine or a slap on a wrist," Drew said. "I believe that the perpetrator deserves the fullest attention of the law."

-Mike Keyserman and Rachel Marder contributed to this article.

Deputy Editor Alexandra Perloe co-wrote a story for the Boston Globe about the threat. Perloe did not contribute to the reporting, editing or placement of this article.

 — This article was edited to remove a student's name, as of April 2024