As heartbreaking as Columbine was, as appalling as Virginia Tech was, and as distressing as the Colorado theater shooting was, the mass school shooting in Newtown, Connecticut brought home something more terrifying to parents.

Not even elementary school kids are safe.

While details are still emerging on the mass shooting at Sandy Hook Elementary on Friday – recent reports say 27 people have died, including 20 children – what seems to be clear is that in many ways it was worse than Columbine, which until Virginia Tech had been considered the worst school shooting in U.S. history.

Kids still learning their numbers and barely able to add and subtract confronted the unimaginable: a gunman carrying a .223 caliber rifle and another firearm entered the school and began firing at small children and teachers. A motive remains unclear, but authorities say the killer, identified as 24-year-old Ryan Lanza, also killed his own mother, a teacher at the school.

At the 1999 Columbine High School shooting, 13 people died and 24 were injured. At the Virginia Tech shooting in 2007, 32 were killed before the shooter killed himself.

The shooting in Columbine, on which Eric Harris and Dylan Klebold killed classmates, teachers and themselves, made parents realize not even schools are a safe place to leave a child.

But the one in Connecticut is certain to take school security to a whole new level because of the age of the children and the number of deaths.  

In Connecticut, a routine school day for 5 to 9-year-olds turned into a scene of horror. At least 18 mothers were told the kids they dropped off at school just hours before had died. 

Mergim Bajraliu, 17, heard the gunshots echo from his home and raced to check on his 9-year-old sister at the school. He said his sister, who was fine, heard a scream come over the intercom at one point. He said teachers were shaking and crying as they came out of the building.

"Everyone was just traumatized," he said.

Fox News contributor Dr. Keith Ablow, a psychiatrist, said the shooting of children so young really pushes school shootings into a new dimension.

“This kind of shock registers with people in yet another way because it seems like the unthinkable keeps moving into the sphere of our reality,” he said.

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