DEVELOPING: Authorities say at least 27 people, including 18 children, were killed Friday when a gunman clad in black military gear opened fire inside a Connecticut elementary school.

A law enforcement official said the shooter, who is dead, was from New Jersey and had ties to Sandy Hook Elementary School in Newtown. Authorities recovered a Glock and Sig Sauer 9mm handgun, but it was unclear who killed the shooter, who wore black combat garb and a military vest.

Local news outlets report that the shooting occurred inside a kindergarten classroom, and that all the pupils in that classroom are unaccounted for. 

An official with knowledge of the situation said the 24-year-old gunman, Ryan Lanza, also had a .223-caliber rifle. The motive is not yet known.

Police said a second man is in custody in connection with the shooting. Witnesses told the Connecticut Post that a handcuffed man, dressed in camouflage, was led out of a nearby woods by officers. 

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