In the northeastern US state of Connecticut where a man has killed his mother at home and then opened fire Friday inside the elementary school where she taught.

The rampage killed 28 people, including 20 young children aged 5 to 10. Eighteen children died at the scene and two later in hospital.

The 20-year-old killer committed suicide at the school, bringing the toll to 28. The attack at Sandy Hook Elementary School, just two weeks before Christmas, is the nation’s second-deadliest school shooting. It’s exceeded only by the Virginia Tech university massacre in 2007, that left 32 dead.

A law enforcement official says authorities investigating the mass shooting have found more guns left by the gunman inside the school than the initial two that had been reported. An investigation is now underway.