The incident occurred at the Sandy Hook Elementary School in Newtown city of Connecticut state.
Connecticut police said "several fatalities" have been reported in the incident though the shooter was now dead.
Wearing all black and carrying two 9mm handguns, the gunman opened fire in the school this morning, sending panic waves around the city.
The incident sent crying children spilling into the school parking lot as frightened parents waited for a word on their kids.
Image: In this photo provided by the Newtown Bee, Connecticut State Police lead children from the Sandy Hook Elementary School in Newtown, Conn., following a reported shooting there Friday, Dec. 14, 2012. (AP Photo/Newtown Bee, Shannon Hicks)