Sandy Hook school massacre rekindles US gun control debate

No one yet knows what transformed nerdy, small-town loner Adam Lanza into a black-clad monster who gunned down 26 people, including 20 young children, at an elementary school.

But as America comes to terms with a massacre whose death toll exceeded that of one of the most notorious US school shootings, the 1999 rampage at Columbine High School massacre, questions will be asked not just about his motive, but also about gun control.

Ahead of US President Barack Obama's visit to Newtown to mourn the dead and console survivors, a top US Democrat said she would introduce a bill banning assault weapons as soon as the new Congress convenes in January.

"I'm going to introduce in the Senate, and the same bill will be introduced in the House, a bill to ban assault weapons," Senator Dianne Feinstein of California told NBC's Meet the Press programme.

Obama's appearance at an interfaith vigil in the once-tranquil town will be watched closely for clues as to what he meant when he called for "meaningful action" to prevent such tragedies in the wake of the massacre on Friday.

For the president, this is the fourth trip of his presidency to a community still grieving from a mass shooting. Just last summer, Obama went to Aurora, Colorado, to visit victims and families after a shooting spree at a cinema left 12 people dead.