State Police received the first 911 call at 9:41 a.m. and immediately began sending emergency units from the western part of the state. Initial 911 calls said multiple students were trapped in a classroom, possibly with a gunman, according to a Connecticut State Police source.
Vance said on-duty and off-duty officers swarmed to the school and quickly checked "every door, every crack, every crevice" in the building looking for the gunman and evacuating children.
Soon, state police from across western Connecticut would be there. And they would be joined by FBI SWAT and evidence teams as well as members of the federal Bureau of Alcohol Tobacco and Firearms.
A photo from the scene showed a line of distressed children being led out of the school.
Three patients were taken to Danbury Hospital, which also went on lockdown, according to the hospital's Facebook page.
"Out of abundance of caution and not because of any direct threat Danbury Hospital is under lockdown," the statement said. "This allows us simply to focus on the important work at hand."
Newtown Public School District secretary of superintendent Kathy June said in a statement that the district's schools were locked down because of the report of a shooting.
"The district is taking preventive measures by putting all schools in lockdown until we ensure the safety of all students and staff," she said.
All public and private schools in the town were on lockdown.
"We have increased our police presence at all Danbury Public Schools due to the events in Newtown. Pray for the victims," Newtown Mayor Mark Boughton tweeted.