Texas teenager had shot grandmother before killing 21 in one classroom

Authorities said the suspect, an 18-year-old boy, was also killed by police. [Courtesy of NDTV]

The 19 children and two teachers massacred at a South Texas elementary school were in a single fourth-grade classroom where the gunman barricaded himself, authorities said on Wednesday as the deadliest school shooting in a nearly decade reignited debate over America's gun laws.

Police circled Robb Elementary School in Uvalde, Texas, breaking windows in an effort to evacuate children and staff, Texas Department of Public Safety spokesperson Chris Olivarez told CNN. Officers eventually breached the classroom and killed the gunman, identified as 18-year-old Salvador Ramos.