"Everyone is safe," Stamford police Lt. Thomas Barcello said when the evacuation was done.
But before the 1,900 students and 200 staff members left the building, officers set up a perimeter around the Strawberry Hill Avenue school and blocked nearby roads.
Police released few details on the call, which came in at about 12:30 p.m. to the school, saying the investigation was "fluid and ongoing."
"We coordinated with the school, the board of ed and the assistant superintendent to get the ball rolling and get all of the students out of the building," police Lt. Diedrich Hohn told reporters. "We coordinated to get everyone into this parking lot [behind the school] for safe-keeping and sent out an automated robocall to parents to come and pick up their children."
Because it was cold and because it was near the end of the school day, the transportation company sent buses to Fenway Street behind the school to pick up students, he said.
The students were all out of the building within a half-hour of the call and the school campus was emptied out within an hour, Hohn said.
Stamford High student Christian Hamilton, who was waiting for a ride at a nearby Dunkin' Donuts, said it was announced over the school's intercom system.
"What I was told was that there was a bomb threat. We were all told to evacuate," Hamilton said.
Barcello said the police department called in additional resources, including the SWAT team, the bomb squad, the fire department and EMS.
The investigation continued into the afternoon after the building was evacuated.
"We are still inside, still clearing the building, making sure there are no threats," Barcello said. "This part of the investigation is ongoing."
The police praised the school community for its responsiveness.
"Kudos to everyone, students and teachers, for taking this seriously," Hohn said. "It was a good practice run should something, God forbid, ever happen."
The incident at Stamford High was not the only one on Tuesday. West Haven High School, and Bristol Central High School and South Side School in Bristol, also received threats.
Tuesday night's basketball game was canceled. There was no word Wednesday classes at Stamford High.
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