The incident was one of the worst mass shootings in U.S. history — 26 people killed, including 20 students ages 6 and 7.
The gunman then shot and killed himself.
The tragic events have sparked concerns of school safety and emergency response plans, but it is clear that vigilance will be high this week at schools around the country.
Cleveland Police Capt. Mike McCain said his heart goes out to the victims' families and all of the Newtown community.
McCain supervises the four-man School Resources Officers unit responsible for the security of 13 campuses within the Cleveland School District.
He said the unit, and the department as a whole, undergoes intense training for rapid response in active shooter situations.
"Ever since the Columbine incident the federal government has made it a priority for all police officers to undergo rapid response gunman training," McCain said. "No matter where we are, we automatically go to where the shooter is and try to take control of the scenario.
"What happened at Sandy Hook was terrible, but the officers responded quickly and the school did well to get into lockdown. Reports are saying the violence ended in about three minutes."
McCain added that gunman response training by the Cleveland Police Department is likely identical to training received by authorities in Newtown.
And to be prepared for school shootings, it takes training, practice and leadership from both the School Resource Officers unit and school administrators.
"We carefully and very seriously practice lockdown routines every couple months at all the schools," said SRO Officer Lamar Tindle.
The lockdown procedure requires teachers to barricade and lock doors, cover windows and gather students in the least visible part of the room.
Custodians are trained to immediately lock school exits to prevent entry of more danger.
Keeping everyone quiet is of utmost significance.
"The most important part is for people to remain calm, whether it's training or a real lockdown situation," said Tindle. "They need to let us come in and do our jobs."
McCain added parents need to be as understanding as possible when real lockdown situations occur.
"We know it's hard for parents to keep their distance when emergencies happen at school but they really need to understand we have a job to do," said McCain. "It's imperative that they stay back and let us do what we are trained to do."
Students at Cleveland High School feel the unit is doing a good job keeping them safe when the enter school each day.
"What happened (in Connecticut) is such a sad situation," said CHS senior Churvondria Baskin. "I'm really thankful we have officers here to protect us at school."
Fellow classmates echoed Baskin's mournfulness.
"In the back of your head there's always the thought that it could happen to any one of us," added senior Jerad Hunt. "I can't even imagine what all the families are going through — thankfully we've never had a tragedy like that here."
"The lives lost means there are so many seniors (in Newtown) who won't graduate, so many weddings that won't take place and so many big ideas that won't be shared," said senior Trace Bray. "The kids who died weren't even old enough to do anything wrong yet."
"We get to have another day to live — they don't have the chance to see what the will become," said senior Brittany Thigpen.
Protecting the future of Cleveland's students is not a responsibility the SRO unit takes lightly.
"We care as much about the students as the parents do," said McCain. "We are here to keep them safe and to make sure they have a bright future."